Writing to File C++

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main() {
    ofstream myfile;
    myfile.open("voffi.txt");

    for (int a = 1; a < 501; a++)
    {
        myfile << "person(" + to_string(a) + ").\n";
    }

    for (int a = 1; a < 501; a++)
    {
        for (int b = a + 1; b < 501; b++)
        {
            myfile << "knows(" + to_string(a) + "," + to_string(b) + ").\n";
        }
    }

    myfile.close();
    return 0;
}