#include <bits/stdc++.h>
using namespace std;
int main() {
  string s1, s2;
  cin >> s1 >> s2;
  string h1, m1, h2, m2;
  h1 = s1[0];
  h1 += s1[1];
  m1 = s1[3];
  m1 += s1[4];
  h2 = s2[0];
  h2 += s2[1];
  m2 = s2[3];
  m2 += s2[4];
  int h11 = 0, m11 = 0, h22 = 0, m22 = 0;
  stringstream geek(h1);
  geek >> h11;
  stringstream gee(m1);
  gee >> m11;
  stringstream gek(h2);
  gek >> h22;
  stringstream eek(m2);
  eek >> m22;
  if (m22 > m11) {
    m11 += 60;
    h11--;
  }
  if (h11 - h22 < 10) {
    if (h11 - h22 == 0)
      cout << "00";
    else {
      if (h11 - h22 < 0 && h11 - h22 > -10)
        cout << (h11 - h22) + 24;
      else if (h11 - h22 < 10 && h11 - h22 > 0)
        cout << "0" << (h11 - h22);
      else {
        h11 -= h22;
        h11 += 24;
        if (h11 < 10)
          cout << "0" << h11;
        else
          cout << h11;
      }
    }
  } else
    cout << (h11 - h22);
  cout << ':';
  if (m11 - m22 < 10) {
    if (m11 - m22 == 0)
      cout << "00";
    else {
      if (m11 - m22 < 0 && m11 - m22 > -10)
        cout << (m11 - m22) + 60;
      else if (m11 - m22 < 10 && m11 - m22 > 0)
        cout << "0" << (m11 - m22);
      else if (m11 - m22 < 10)
        cout << (m11 - m22);
      else
        cout << "0" << (m11 - m22);
    }
  } else
    cout << (m11 - m22);
  return 0;
}
