#include<cstdio>
const int CLK_TCK=100;int main(){
//1.读入c1,c2int  c1,c2;scanf("%d%d",&c1,&c2);
//2.定义常量CLK_TCK=100
//难点：不足 1 秒的时间四舍五入到秒	--不用round()，避免浮点数运算 int dif = c2-c1;if(dif%100>=50){dif = dif/100+1;}else{dif = dif/100;}
//3.难点：将C2-C1换算成hh:mm:ss
//1h=60min=3600s;1min=60sint hh,mm,ss;hh = dif/3600;mm = dif%3600/60;ss = dif%3600%60;
//4.输出--高位为空，用0填充 printf("%02d:%02d:%02d",hh,mm,ss); return 0;
}