#include <stdio.h>
int main ()
{
int a = 0;
int b = 0;
int c = 0;
int d = 0;
int e = 0;
scanf ("%d %d %d %d %d\n",&a,&b,&c,&d,&e);
printf ("%.1f",(a+b+c+d+e)/5.0);
    return 0;
}