include<stdio.h>
int main()
{
float x,y;
scanf("%f %f",&x,&y);
if(((int)x%5==0) && (x + .5 <= y))
printf(".2f",y-x-.5);
else
printf(".2f",y);
return 0;
}
int main()
{
float x,y;
scanf("%f %f",&x,&y);
if(((int)x%5==0) && (x + .5 <= y))
printf(".2f",y-x-.5);
else
printf(".2f",y);
return 0;
}