Nothing interesting

#include <iostream>
#include <sstream>

using namespace std;

string num_to_str(int num)
{
    stringstream s;
    s << num;
    string a = s.str();
    return a;
}
int main ()
{
    int num0, num5;
    string num;
    int counter = 0;
    for(int i = 100005;i<=999500;i++)
    {
        num0 = 0;
        num5 = 0;
        num = num_to_str(i);
        for(int j = 0;j<6;j++)
        {
            if(num[j] == '0') num0++;
            if(num[j] == '5') num5++;
        }
        if(num0 >= 3 && num5 >= 1)
        {
            counter++;
            cout << i << endl;
        }
    }
    cout << endl << "ilosc: " << counter << endl;
    return 0;
}