Программирование C++ Помогите решить задачу

Задача для школьника

#include <iostream>
#include <string>
#include <cstdlib>
using namespace std;
class Time {
public:
Time() : h(0), m(0), s(0) {}
Time(const int s) : h(s / 3600), m((s - h * 3600) / 60), s(s % 60) {}
Time(const int h, const int m, const int s) : h(h), m(m), s(s) {}
string time_string()const {
string time = h < 10 ? "0" : "";
time += to_string(h) + ":" + (m < 10 ? "0" : "");
time += to_string(m) + ":" + (s < 10 ? "0" : "");
time += to_string(s);
return time;
}
private:
int h;
int m;
int s;
friend ostream& operator<<(ostream& out, const Time& t) {
return out << t.time_string();
}
};
int main() {
cout << "Seconds: ";
int sec;
cin >> sec;
Time time{ sec };
cout << "Time: " << time << '\n';
system("pause > nul");
}

#include <iostream>
using namespace std; int main()
{ int n, h, m, s; cout << "n » "; cin >> n;
h = n / 3600; n -= h * 3600; m = n / 60;
n -= m * 60; cout << h << "h:" << m << "m:" <<
n % 60 << "s" << endl; system("pause > nul"); }