#include <bits/stdc++.h>
using namespace std;

int main()
{
    int s,v;
    cin >> s >> v;
    int tim_h = 7,tim_m = 50;
    double tim = s * 1.0 / v;
    int t = s*1.0/v;
    int tim_h2 = tim / 60,tim_m2 = t % 60;
    tim_h -= tim_h2;
    if(tim_m - tim_m2 < 0)
    {
    	tim_m += 60;
    	tim_h--;
    }
    tim_m -= tim_m2;
    if(tim_h < 10) cout << "0" << tim_h << ":" << tim_m-1 << endl;
    if(tim_m < 10) cout << "0" << tim_h << ":0" << tim_m-1 << endl;
    return 0;
}