diff --git a/src/problem1.js b/src/problem1.js
index 9a14f2c..6af7f9e 100644
--- a/src/problem1.js
+++ b/src/problem1.js
@@ -1,6 +1,41 @@
 function problem1(pobi, crong) {
   var answer;
+  if ((pobi[0] + 1 !== pobi[1])
+    || (crong[0] + 1 !== crong[1])
+    || (pobi[0] < 1 || pobi[0] > 400)
+    || (crong[0] < 1 || crong[0] > 400)) {
+    return -1;
+  }
+  const pobimax = getMax(pobi);
+  const crongmax = getMax(crong);
+  if (pobimax > crongmax) answer = 1;
+  else if (pobimax < crongmax) answer = 2;
+  else answer = 0;
   return answer;
 }
 
-module.exports = problem1;
+function getMax(_arr) {
+  const arr=[];
+  for (let _a of _arr) {
+    let a=_a;
+    const row=[];
+    while (a > 0) {
+      row.push(a % 10);
+      a = Math.floor(a / 10);
+    }
+    arr.push(row);
+  }
+  const maxArr=[];
+  for (let row of arr) {
+    let sum=0;
+    let mul=1;
+    for (let n of row) {
+      sum += n;
+      mul *= n;
+    }
+    maxArr.push(sum, mul);
+  }
+  return Math.max(...maxArr);
+}
+
+module.exports = problem1;
\ No newline at end of file
diff --git a/src/problem2.js b/src/problem2.js
index cebd07c..28daeaa 100644
--- a/src/problem2.js
+++ b/src/problem2.js
@@ -1,6 +1,16 @@
 function problem2(cryptogram) {
   var answer;
+  let i=0;
+  answer = cryptogram;
+  while (i<answer.length-1) {
+    if (answer[i] === answer[i+1]) {
+      answer = answer.slice(0,i) + answer.slice(i+2);
+      i=0;
+      continue;
+    }
+    i++;
+  }
   return answer;
 }
 
-module.exports = problem2;
+module.exports = problem2;
\ No newline at end of file
diff --git a/src/problem3.js b/src/problem3.js
index 1baed28..a2964d3 100644
--- a/src/problem3.js
+++ b/src/problem3.js
@@ -1,5 +1,19 @@
 function problem3(number) {
   var answer;
+  answer = 0;
+  for (let i = 1; i <= number; i++) {
+    n=i;
+    while (n>0) {
+      r=n%10;
+      if (r === 3
+        || r === 6
+        || r === 9
+      ) {
+        answer++;
+      }
+      n=Math.floor(n/10);
+    }
+  }
   return answer;
 }
 
diff --git a/src/problem4.js b/src/problem4.js
index ee1d3bd..8321360 100644
--- a/src/problem4.js
+++ b/src/problem4.js
@@ -1,5 +1,18 @@
 function problem4(word) {
   var answer;
+  answer = "";
+  for ( c of word ) {
+    let a;
+    if ( c>="A" && c<="Z" ) {
+      a = String.fromCharCode( "Z".charCodeAt(0) - ( c.charCodeAt(0) - "A".charCodeAt(0) ) );
+      answer+=a;
+    }  else if ( c>="a" && c<="z" ) {
+      a = String.fromCharCode( "z".charCodeAt(0) - ( c.charCodeAt(0) - "a".charCodeAt(0) ) );
+      answer+=a;
+    } else {
+      answer+=c;
+    }
+  }
   return answer;
 }
 
diff --git a/src/problem5.js b/src/problem5.js
index 9368e87..e27bc5e 100644
--- a/src/problem5.js
+++ b/src/problem5.js
@@ -1,5 +1,11 @@
 function problem5(money) {
   var answer;
+  answer = [];
+  const coinTypes = [50000, 10000, 5000, 1000, 500, 100, 50, 10, 1];
+  for (let c of coinTypes) {
+    answer.push(Math.floor(money / c));
+    money = money % c;
+  }
   return answer;
 }
 
diff --git a/src/problem6.js b/src/problem6.js
index 3f842b5..ea38974 100644
--- a/src/problem6.js
+++ b/src/problem6.js
@@ -1,6 +1,29 @@
 function problem6(forms) {
   var answer;
-  return answer;
+  answer = [];
+  for (let i = 0; i < forms.length; i++) {
+    for (let j = i + 1; j < forms.length; j++) {
+      if (checkSimilar(forms[i][1], forms[j][1])) {
+        if (!answer.includes(forms[i][0])) {
+          answer.push(forms[i][0]);
+        }
+        if (!answer.includes(forms[j][0])) {
+          answer.push(forms[j][0]);
+        }        
+      }
+    }
+  }
+  return answer.sort();
+}
+function checkSimilar(_name1, _name2) {
+  for (let i = 1; i < _name1.length; i++) {
+    for (let j = 1; j < _name2.length; j++) {
+      if ((_name1[i-1] === _name2[j-1])
+        && (_name1[i] === _name2[j])) {
+        return true;
+      }
+    }
+  }
+  return false;
 }
-
 module.exports = problem6;
diff --git a/src/problem7.js b/src/problem7.js
index ee1bb9d..779410a 100644
--- a/src/problem7.js
+++ b/src/problem7.js
@@ -1,5 +1,51 @@
 function problem7(user, friends, visitors) {
   var answer;
+  let score = new Map();
+  let userFriends = [];
+  for (let f of friends) {
+    if (f[1] === user) {
+      userFriends.push(f[0]);
+    } else if (f[0] === user) {
+      userFriends.push(f[1]);
+    }
+  }
+  for (let f of friends) {
+    if (userFriends.includes(f[0]) 
+      && f[1] !== user 
+      && !userFriends.includes(f[1])) {
+        if (score.has(f[1])) {
+          score.set(f[1], score.get(f[1]) + 10);
+        } else {
+          score.set(f[1], 10);
+        }
+    } else if (userFriends.includes(f[1]) 
+      && f[0] !== user 
+      && !userFriends.includes(f[0])) {
+        if (score.has(f[0])) {
+          score.set(f[0], score.get(f[0]) + 10);
+        } else {
+          score.set(f[0], 10);
+        }
+    }
+  }
+  for (let v of visitors) {
+    if (v !== user && !userFriends.includes(v)) {
+      if (score.has(v)) {
+        score.set(v, score.get(v) + 1);
+      } else {
+        score.set(v, 1);
+      }
+    }
+  }
+  arr = Array.from(score);
+  arr.sort((a, b) => (b[1] - a[1])
+    || a[0].localeCompare(b[0]));
+  answer = [];
+  const n = arr.length > 5 ? 5 : arr.length;
+  for (let i = 0; i < n; i++) {
+    answer.push(arr[i][0]);
+  }
+
   return answer;
 }