piwo cza

#include <bits/stdc++.h>

using namespace std;

int main()
{
    string s, t;
    cin>>s;
    cin>>t;
    int sH = stoi(s.substr(0, 2));
    int sM = stoi(s.substr(3, 2));
    int tH = stoi(t.substr(0, 2));
    int tM = stoi(t.substr(3, 2));
    int deltaH, deltaM = 0;

    deltaH = sH - tH;
    if(deltaH < 0) deltaH += 24;

    deltaM = sM - tM;
    if(deltaM < 0){
        deltaM += 60;
        deltaH--;
    }

    if(deltaH < 0) deltaH += 24;

    string outH = to_string(deltaH);
    if(outH.length() < 2) outH = "0" + outH;

    string outM = to_string(deltaM);
    if(outM.length() < 2) outM = "0" + outM;

    cout << outH + ":" + outM << endl;

    return 0;
}