diff --git a/CMakeLists.txt b/CMakeLists.txt
index 207fc79..3a46dd4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,40 +4,40 @@ project(PE-Fortran VERSION 0.0.4
   HOMEPAGE_URL https://github.com/han190/PE-Fortran
   LANGUAGES Fortran)
 
-if (CMAKE_Fortran_COMPILER_ID STREQUAL "GNU")
+if (CMAKE_SYSTEM_NAME STREQUAL "Linux" OR CMAKE_SYSTEM_NAME STREQUAL "Darwin")
+  if (CMAKE_Fortran_COMPILER_ID STREQUAL "GNU")
+    if (CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 9.0)
+      message(FATAL_ERROR gfortran >= ${CMAKE_Fortran_COMPILER_VERSION})
+    endif()
+    message(STATUS "Using gfortran ${CMAKE_Fortran_COMPILER_VERSION}.")
 
-  if (CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 9.0)
-    message(FATAL_ERROR gfortran >= ${CMAKE_Fortran_COMPILER_VERSION})
+    if (CMAKE_BUILD_TYPE STREQUAL "Debug")
+      message(STATUS "Compiling in debug mode.")
+      set(CMAKE_Fortran_FLAGS "-g -O0 -Wall -Wextra -pedantic -fbounds-check \
+        -fimplicit-none -fPIC -Wno-uninitialized -fcheck=all -fbacktrace \
+        -ffree-form -fcheck=array-temps -Werror=implicit-interface \
+        -std=f2018 -march=native")
+    elseif (CMAKE_BUILD_TYPE STREQUAL "Release")
+      message(STATUS "Compiling in release mode.")
+      set(CMAKE_Fortran_FLAGS "-O3 -march=native -std=f2018 -march=native")
+    endif()
+  elseif (CMAKE_Fortran_COMPILER_ID STREQUAL "IntelLLVM")
+    if (CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 2021.11)
+      message(FATAL_ERROR ifx >= ${CMAKE_Fortran_COMPILER_VERSION})
+    endif()
+    message(STATUS "Using ifx ${CMAKE_Fortran_COMPILER_VERSION}.")
+      
+    if (CMAKE_BUILD_TYPE STREQUAL "Debug")
+      message(STATUS "Compiling in debug mode.")
+      set(CMAKE_Fortran_FLAGS "-O0 -warn all -check all,nouninit \
+        -g -traceback -no-simd -stand f18 -mtune=native")
+    elseif (CMAKE_BUILD_TYPE STREQUAL "Release")
+      message(STATUS "Compiling in release mode.")
+      set(CMAKE_Fortran_FLAGS "-O1 -ipo -xHost -stand f18 -mtune=native")
+    endif()
   endif()
-  message(STATUS "Using gfortran ${CMAKE_Fortran_COMPILER_VERSION}.")
-
-  if (CMAKE_BUILD_TYPE STREQUAL "Debug")
-    message(STATUS "Compiling in debug mode.")
-    set(CMAKE_Fortran_FLAGS "-g -O0 -Wall -Wextra -pedantic -fbounds-check \
-      -fimplicit-none -fPIC -Wno-uninitialized -fcheck=all -fbacktrace \
-      -ffree-form -fcheck=array-temps -Werror=implicit-interface \
-      -std=f2018 -march=native")
-  elseif (CMAKE_BUILD_TYPE STREQUAL "Release")
-    message(STATUS "Compiling in release mode.")
-    set(CMAKE_Fortran_FLAGS "-O3 -march=native -std=f2018 -march=native")
-  endif()
-
-elseif (CMAKE_Fortran_COMPILER_ID STREQUAL "IntelLLVM")
-
-  if (CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 2021.11)
-    message(FATAL_ERROR ifx >= ${CMAKE_Fortran_COMPILER_VERSION})
-  endif()
-  message(STATUS "Using ifx ${CMAKE_Fortran_COMPILER_VERSION}.")
-    
-  if (CMAKE_BUILD_TYPE STREQUAL "Debug")
-    message(STATUS "Compiling in debug mode.")
-    set(CMAKE_Fortran_FLAGS "-O0 -warn all -check all,nouninit \
-      -g -traceback -no-simd -stand f18 -mtune=native")
-  elseif (CMAKE_BUILD_TYPE STREQUAL "Release")
-    message(STATUS "Compiling in release mode.")
-    set(CMAKE_Fortran_FLAGS "-O1 -ipo -xHost -stand f18 -mtune=native")
-  endif()
-
+else()
+  message(FATAL_ERROR "Unsupported OS.")
 endif()
 
 # Build static library
diff --git a/Makefile b/Makefile
deleted file mode 100644
index a73a774..0000000
--- a/Makefile
+++ /dev/null
@@ -1,112 +0,0 @@
-compiler?=gfortran
-profile?=release
-src_dir:=src
-current_dir=$(dir $(realpath $(lastword $(MAKEFILE_LIST))))
-build_dir=$(current_dir)build/$(compiler)_$(profile)_makefile
-data_dir=$(current_dir)data
-include_dir=$(build_dir)/include
-local_dir=${HOME}/.local
-prefix=$(local_dir)/bin
-data_prefix=$(local_dir)/share/PE-Fortran-data
-args?=
-
-ifeq ($(compiler), gfortran)
-	compiler_flags=-std=f2018 -march=native
-	ifeq ($(profile), debug)
-		compiler_flags+=-g -O0 -Wall -Wextra -pedantic -fbounds-check \
-			-fimplicit-none -fPIC -Wno-uninitialized -fcheck=all -fbacktrace \
-			-ffree-form -fcheck=array-temps -Werror=implicit-interface
-	else ifeq ($(profile), release)
-		compiler_flags+=-O3 -march=native
-	endif
-	compile=$(compiler) $(compiler_flags) \
-		-I$(include_dir) -J$(build_dir)
-else ifeq ($(compiler), ifx)
-	compiler_flags=-stand f18 -mtune=native
-	ifeq ($(profile), debug)
-		compiler_flags+=-O0 -warn all -check all,nouninit -g -traceback -no-simd
-	else ifeq ($(profile), release)
-		compiler_flags+=-O1 -ipo -xHost
-	endif
-	compile=$(compiler) $(compiler_flags) \
-		-I$(include_dir) -module $(build_dir)
-	AR=xiar
-endif
-
-# Preprocess objects
-preproc_filename=module_file module_preprocessor preprocess
-preproc_dir=$(src_dir)/preprocess
-preproc_obj=$(addprefix $(build_dir)/, \
-	$(addsuffix .o, $(preproc_filename)))
-
-# Toolkit objects
-toolkit_filename=module_utility module_quicksort module_prime \
-	module_permutation module_multiprecision module_list module_toolkit
-toolkit_dir=$(src_dir)/toolkit
-toolkit_obj=$(addprefix $(build_dir)/, \
-	$(addsuffix .o, $(toolkit_filename)))
-
-# Problems objects
-problems_dir=$(src_dir)/problems
-problems_src=$(wildcard $(problems_dir)/*.f90)
-problems_obj=$(subst $(problems_dir), $(build_dir), \
-	$(patsubst %.f90, %.o, $(problems_src)))
-
-# PE objects
-pe_filename=module_problem module_driver project_euler
-pe_obj=$(addprefix $(build_dir)/, $(addsuffix .o, $(pe_filename)))
-
-.PHONY: clean build preprocess install test
-all: $(build_dir)/PE-Preprocess preprocess \
-	$(build_dir)/libpetk.a $(build_dir)/PE-Fortran
-
-test:
-	$(build_dir)/PE-Fortran -d $(data_dir) $(args)
-
-install:
-	mkdir -p $(data_prefix)
-	mkdir -p $(prefix)
-	cp $(data_dir)/* $(data_prefix)
-	cp $(build_dir)/PE-Preprocess $(prefix)
-	cp $(build_dir)/PE-Fortran $(prefix)
-	@echo Executables installed to $(prefix)
-	@echo Data copied to $(data_prefix)
-	@echo PE-Fortran is installed successfully.
-
-$(build_dir)/PE-Fortran: $(pe_obj) $(problems_obj)
-	$(compile) -o $@ $(pe_obj) $(problems_obj) -L$(build_dir) -lpetk
-	@echo PE-Fortran is built successfully.
-
-$(build_dir)/%.o: $(src_dir)/%.f90
-	$(compile) -c $< -o $@
-
-$(build_dir)/%.o: $(problems_dir)/%.f90
-	$(compile) -c $< -o $@
-
-libs: $(build_dir)/libpetk.a
-$(build_dir)/libpetk.a: $(toolkit_obj)
-	$(AR) rcs $@ $(toolkit_obj)
-
-$(build_dir)/%.o: $(toolkit_dir)/%.f90
-	$(compile) -c $< -o $@
-
-preprocess:
-	$(build_dir)/PE-Preprocess -d $(data_prefix) -i $(include_dir)
-
-$(build_dir)/PE-Preprocess: $(preproc_obj)
-	$(compile) -o $@ $(preproc_obj)
-
-$(build_dir)/%.o: $(preproc_dir)/%.f90 build
-	$(compile) -c $< -o $@
-
-build:
-	mkdir -p $(build_dir) $(include_dir)
-
-clean:
-	$(RM) -r $(build_dir)
-	@echo Build files cleaned.
-
-uninstall:
-	$(RM) $(prefix)/PE-Fortran $(prefix)/PE-Preprocess
-	$(RM) -r $(data_prefix)
-	@echo PE-Fortran uninstalled.
diff --git a/src/module_driver.f90 b/src/module_driver.f90
index 376db8d..442aa92 100644
--- a/src/module_driver.f90
+++ b/src/module_driver.f90
@@ -94,9 +94,10 @@ end function problem_found
 
 !> Get arugment
 subroutine get_arguments()
-  character(len=:), allocatable :: answer_sheet, data_directory, output_format
-  character(len=:), allocatable :: arguments(:), keywords(:)
-  character(len=:), allocatable :: argument, next_argument, messages(:)
+  character(len=:), allocatable :: answer_directory, data_directory
+  character(len=:), allocatable :: keywords(:), messages(:)
+  character(len=:), allocatable :: arguments(:), argument, next_argument
+  character(len=:), allocatable :: output_format
   integer(int64) :: num_trails, selected
   integer :: argument_counts, i
   type(problem_type), allocatable :: problems(:)
@@ -112,8 +113,8 @@ subroutine get_arguments()
 
   !> Default values
   data_directory = default_data_directory
-  allocate (character(len=500) :: answer_sheet)
-  answer_sheet = "answer.log"
+  allocate (character(len=500) :: answer_directory)
+  answer_directory = "."
   num_trails = 2
   selected = 0
   list_solved = .false.
@@ -146,9 +147,9 @@ subroutine get_arguments()
       output_format = "('Data directory:', 1x, a)"
       write (output_unit, output_format) trim(data_directory)
     case ("-a", "--answer")
-      answer_sheet = next_argument
-      output_format = "('Answer sheet:', 1x, a)"
-      write (output_unit, output_format) trim(answer_sheet)
+      answer_directory = next_argument
+      output_format = "('Answer directory:', 1x, a)"
+      write (output_unit, output_format) trim(answer_directory)
     case ("-l", "--list")
       list_solved = .true.
     case ("-v", "--version")
@@ -177,7 +178,8 @@ subroutine get_arguments()
     return
   end if
   call solve_problems(problems, num_trails, selected)
-  if (selected == 0) call print_answers(problems, trim(answer_sheet))
+  if (selected == 0) call print_answers( &
+    & problems, trim(answer_directory)//"/answer.log")
 end subroutine get_arguments
 
 end module module_driver