#include <iostream>
using namespace std;
int rez,a1,a2,b1,b2,c1,c2;
char k;
int main()
{
   cin >>a1>>k>>b1>>k>>c1;
   cin >>a2>>k>>b2>>k>>c2;
   b1+=a1*60;
   c1+=b1*60;
   b2+=a2*60;
   c2+=b2*60;
   rez=c2-c1;
   if (rez==0) {rez=24*60*60;}
   if (rez<0) {rez+=24*60*60;}
   b1=rez/60;
   c1=rez%60;
   a1=b1/60;
   b1=b1%60;
   if (a1<10) {cout<<0;}
   cout <<a1<<":";
   if (b1<10) {cout<<0;}
   cout <<b1<<":";
   if (c1<10) {cout<<0;}
   cout <<c1;
}