#include <bits/stdc++.h>
#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize("Ofast")
namespace ringo {
template <class T>
inline void read(T &x) {
  x = 0;
  register char c = getchar();
  register bool f = 0;
  while (!isdigit(c)) f ^= c == '-', c = getchar();
  while (isdigit(c)) x = x * 10 + c - '0', c = getchar();
  if (f) x = -x;
}
template <class T>
inline void print(T x) {
  if (x < 0) putchar('-'), x = -x;
  if (x > 9) print(x / 10);
  putchar('0' + x % 10);
}
template <class T>
inline void maxd(T &a, T b) {
  if (b > a) a = b;
}
template <class T>
inline void mind(T &a, T b) {
  if (b < a) a = b;
}
template <class T>
inline void print(T x, char c) {
  print(x), putchar(c);
}
template <class T>
inline T abs(const T &a) {
  if (a < 0) return -a;
  return a;
}
int s, t, p;
std::string strs, strt, strp;
void main() {
  std::cin >> strt >> strs;
  s = 600 * (strs[0] - '0') + 60 * (strs[1] - '0') + 10 * (strs[3] - '0') +
      strs[4] - '0';
  t = 600 * (strt[0] - '0') + 60 * (strt[1] - '0') + 10 * (strt[3] - '0') +
      strt[4] - '0';
  p = t - s < 0 ? t - s + 1440 : t - s;
  putchar(p / 600 + '0');
  p %= 600;
  putchar(p / 60 + '0');
  p %= 60;
  putchar(':');
  putchar(p / 10 + '0');
  p %= 10;
  putchar(p + '0');
  putchar('\n');
}
}  // namespace ringo
signed main() { return ringo::main(), 0; }
