```
#include <bits/stdc++.h>
using namespace std;
int main(){
int s,v,z=470,a,b;
cin>>s>>v;
if(s%v!=0)s+=v;
s=s/v;
z-=s;
if(z<0)z+=1440;
a=z/60;
b=z%60;
if(a<10)cout<<'0';
cout<<a<<':';
if(b<10)cout<<'0';
cout<<b;
}
```
by zjhzs666 @ 2023-03-21 13:24:13