#include<iostream>
#include<math.h>
using namespace std;
int main(int argc, char const *argv[])
{
   int c1,c2 = 0;
   cin >> c1 >> c2;
   int ans = (c2-c1);
   //用于四舍五入进位，减少浮点数运算
   if(ans%100 >= 50){
       ans = ans/100 + 1;
   }else{
       ans = ans/100;
   }
   //不够补0
   printf("%02d:%02d:%02d",ans/3600,ans%3600/60,ans%3600%60);
   return 0;
}