#include <stdio.h>
void main()
{
     int x,a;
     float y;
     scanf("%d",&x);
     a=x/15;
     switch(a)
     {
     case 0: y=40.0/15.0*x+10;printf("y=%f",y);break;
     case 1: y=50;printf("y=%f",y);break;
     case 2: y=50-10.0/15.0*(x-30);printf("y=%f",y);break;
     case 3:
     case 4: y=40+20.0/30.0*(x-45);printf("y=%f",y);break;
     case 5: y=60-10.0/15.0*(x-75);printf("y=%f",y);break;
     default:printf("no meaning\n");
     }
}