#include <bits/stdc++.h>
using namespace std;
int main() {
  int mini, segi;
  string asd;
  getline(cin, asd);
  mini = 10 * (asd[0] - '0') + asd[1] - '0';
  segi = 10 * (asd[3] - '0') + asd[4] - '0';
  int mindor, segdor;
  getline(cin, asd);
  mindor = 10 * (asd[0] - '0') + asd[1] - '0';
  segdor = 10 * (asd[3] - '0') + asd[4] - '0';
  int tiemp = 60 * mini + segi - 60 * mindor - segdor;
  if (tiemp < 0) {
    tiemp += 24 * 60;
  }
  int minfin = tiemp / 60;
  int segin = tiemp % 60;
  if (minfin == 0) {
    cout << "00:";
    if (segin == 0) {
      cout << "00";
    } else if (log10(segin) < 1) {
      cout << "0" << segin;
    } else {
      cout << segin;
    }
  } else if (log10(minfin) < 1) {
    cout << "0" << minfin << ":";
    if (segin == 0) {
      cout << "00";
    } else if (log10(segin) < 1) {
      cout << "0" << segin;
    } else {
      cout << segin;
    }
  } else {
    cout << minfin << ":";
    if (segin == 0) {
      cout << "00";
    } else if (log10(segin) < 1) {
      cout << "0" << segin;
    } else {
      cout << segin;
    }
  }
  cout << endl;
  return 0;
}
