#include<stdio.h>
int main()
{
    int v,s;
    int hour,minute,t;
    scanf("%d %d",&s,&v);
    t=480-1.0*s/v; 
    t=t-10;
  if(t<0)
    {
        t=t+24*60;
    }
       hour=t/60;
       minute=t%60;
       if(hour<10)
       {if(minute>=10)
        printf("0%d:%d",hour,minute);
        else        
        printf("0%d:0%d",hour,minute);
        }       
       else if(minute>=10)
       printf("%d:%d",hour,minute);
       else
       printf("%d:0%d",hour,minute);
       return 0;
       }