diff --git a/main.cpp b/main.cpp
index e909509..1e1d52c 100644
--- a/main.cpp
+++ b/main.cpp
@@ -5,45 +5,81 @@
 #include <string>
 #include <sstream>
 #include <vector>
+#include <iomanip>
 #include "person.h"
 #include "utils.h"
+#include "stacks/expressions_calculator.h"
 
 using namespace utils;
 using namespace std;
-
-void init_people_queue(priority_queue<Person> *people_queue, int n) {
-  for (int i = 0; i < n; i++) {
-    int age = generateRandomInt(1,100);
-    ostringstream oss;
-    oss << 2025-age << "-" << generateRandomInt(1,12) << "-" << generateRandomInt(1,30);
-    string birthdate = oss.str();
-    Person new_person(generateRandomName(10), age, birthdate);
-    people_queue->push(new_person);
+void fill_people_queue(priority_queue<Person>* pq_ptr, int total) {
+  for (int idx = 0; idx < total; idx++) {
+    int years = generateRandomInt(1,100);
+    ostringstream date_stream;
+    date_stream << 2025-years << "-" << generateRandomInt(1,12) << "-" << generateRandomInt(1,30);
+    string bdate = date_stream.str();
+    Person person(generateRandomName(6), years, bdate);
+    pq_ptr->push(person);
   }
 }
-
-int main() {
-    std::priority_queue<Person> people_by_age;
-
-    init_people_queue(&people_by_age, 10);
-    
-    while (!people_by_age.empty()) {
-      Person p = people_by_age.top();
-      p.displayInfo();
-      people_by_age.pop();
-    }
-
-    std::priority_queue<Person> people_by_birthday; // or maybe here
-
-    // you need something here
-
-    init_people_queue(&people_by_birthday, 10);
-
-    while (!people_by_birthday.empty()) {
-      Person p = people_by_birthday.top();
-      p.displayInfo();
-      people_by_birthday.pop();
+template<typename PQ>
+void fill_people_queue_custom(PQ& pq, int total) {
+  for (int idx = 0; idx < total; idx++) {
+    int years = generateRandomInt(1,100);
+    ostringstream date_stream;
+    date_stream << 2025-years << "-" << generateRandomInt(1,12) << "-" << generateRandomInt(1,30);
+    string bdate = date_stream.str();
+    Person person(generateRandomName(6), years, bdate);
+    pq.push(person);
+  }
+}
+struct CompareBirthday {
+  bool operator()(const Person& pa, const Person& pb) const {
+    auto extract_month_day = [](const string& bdate) {
+      int year=0,month=0,day=0;
+      char sep;
+      istringstream iss(bdate);
+      iss >> year >> sep >> month >> sep >> day;
+      return month*100+day;
+    };
+    int key_a = extract_month_day(pa.getBirthdate());
+    int key_b = extract_month_day(pb.getBirthdate());
+    return key_a > key_b;
+  }
+};
+int main(int argc, char** argv) {
+  if (argc > 1) {
+    string expression = argv[1];
+    try {
+      auto postfix_expr = expr_calc::infix_to_postfix(expression);
+      double final_result = expr_calc::evaluate_postfix(postfix_expr);
+      string compact_str = expr_calc::postfix_to_compact_string(postfix_expr);
+      cout << "Infix expression   : " << expression << "\n";
+      cout << "Postfix expression : " << compact_str << "\n";
+      cout << "Final Result       : " << setprecision(15) << final_result << "\n";
+    } catch (const exception& exc) {
+      cerr << "Error processing expression: " << exc.what() << "\n";
+      return 1;
     }
+    return 0;
+  }
+  priority_queue<Person> age_queue;
+  fill_people_queue(&age_queue, 10);
+  cout << "People prioritized by AGE (top = largest age):\n";
+  while (!age_queue.empty()) {
+    Person person = age_queue.top();
+    person.displayInfo();
+    cout << "--------------------------\n";
+    age_queue.pop();
+  }
+  priority_queue<Person, vector<Person>, CompareBirthday> birthday_queue;
+  fill_people_queue_custom(birthday_queue, 10);
+  cout << "\nPeople prioritized by BIRTHDAY (top = earliest month-day):\n";
+  while (!birthday_queue.empty()) {
+    Person person = birthday_queue.top();
+    person.displayInfo();
+    cout << "--------------------------\n";
+    birthday_queue.pop();
+  }
+  return 0;
 }
-
-