Почему программа выдает ошибку?

#include <string>
#include <iostream>
#include <cstdlib>
#include <sys/stat.h>
#include <sys/types.h>
#include <sstream>
#include <fstream>
 
// Made by Kawaii >^.^<
namespace patch {
    template <typename T>
    std::string to_string(const T& n) {
        std::ostringstream stm;
        stm << n;
        return stm.str();
    }
}
int main();
class Phones {
    public:
        Phones(int number, std::string name) {
            this->number = number;
            this->name = name;
        }
        void writeInfo(std::string path) {
            std::ofstream save;
            save.open(path + this->name + ".txt");
            save << this->name + "\n" + patch::to_string(this->number);
            save.close();
        }
        void readInfo(std::string path) {
            std::cout << "Name: " + this->name << std::endl;
            std::cout << "Number: " + patch::to_string(this->number) << std::endl;
            for (int i = 0; i < 15; i++) {
                std::cout << "-";
            }
            std::cout << "\n";
        }
    private:
        int number;
        std::string name;
};
 
void options() {
    std::cout << "1 -> Save a new contact" << std::endl;
    std::cout << "2 -> Delete a contact" << std::endl;
    std::cout << "3 -> Edit a contact" << std::endl;
    std::cout << "4 -> Watch a contact" << std::endl;
    std::cout << "5 -> Exit the Program" << std::endl;
}
void newInfo(std::string path) {
    std::string name;
    std::cout << "Contact Name to Edit: ";
    std::cin >> name;
    std::string newName;
    int newNumber;
    std::cout << "New Contact Name: ";
    std::cin >> newName;
    std::ifstream exist(path + name + ".txt");
    if (exist.is_open()) {
        std::cout << "New Contact Number: ";
        std::cin >> newNumber;
        std::ofstream save;
        save.open(path + newName + ".txt");
        save << newName + "\n" + patch::to_string(newNumber);
        save.close();
        std::cout << "-- Contact Edited Successfully --" << std::endl;
    }
    else {
        std::cout << "-- Contact doesn't exists, Try again --" << std::endl;
    }
    exist.close();
    remove((path + name + ".txt").c_str());
}
void activity(int choice, std::string path) {
    int number;
    std::string name;
    if (choice == 1) {
        std::cout << "Contact Name: ";
        std::cin >> name;
        std::cout << "Contact Number: ";
        std::cin >> number;
        std::ifstream exist(path + name + ".txt");
        if (exist.is_open()) {
            std::cout << "-- Contact already exists, Try another name --" << std::endl;
        }
        else {
            Phones cont(number, name);
            cont.writeInfo(path);
            std::cout << "-- Contact Created Successfully --" << std::endl;
        }
    }
    else if (choice == 2) {
        std::cout << "Contact Name to delete: ";
        std::cin >> name;
        remove((path + name + ".txt").c_str());
        std::ifstream exist(path + name + ".txt");
        if (exist.is_open()) {
            std::cout << "-- Error trying to delete, Try again --" << std::endl;
        }
        else {
            std::cout << "-- Contact deleted Successfully --" << std::endl;
        }
    }
    else if (choice == 3) {
        newInfo(path);
    }
    else if (choice == 4) {
        int x = 0;
        std::string info[2];
        std::string line;
        std::cout << "Contact Name to Search: ";
        std::cin >> name;
        std::ifstream exist(path + name + ".txt");
        if (exist.is_open()) {
            while (std::getline(exist, line)) {
                info[x] = line;
                x++;
            }
            int num = atoi(info[1].c_str());
            Phones cont(num, info[0]);
            cont.readInfo(path);
        }
        else {
            std::cout << "-- Contact doesn't exist --" << std::endl;
        }
        exist.close();
    }
}
void _choice(int choice, std::string path) {
    while (true) {
        if (choice == 5) {
            std::cout << "-- Thanks for using --" << std::endl;
            break;
        }
        else {
            activity(choice, path);
            std::cout << "Your Choice: ";
            std::cin >> choice;
        }
    }
}
int main() {
    std::string path = "C:\\Phones\";
    struct stat st;
    if (stat("C:\\Phones", &st) == 0) {
        if (st.st_mode & S_IFDIR != 0) {
        }
    }
    else {
        system("mkdir C:\\Phones");
    }
    options();
    int choice;
    std::cout << "Your Choice: ";
    std::cin >> choice;
    _choice(choice, path);
    return 0;
}