#include<stdio.h>

int main()
{
    double a, b, c, d, e = 0.00;
    scanf("%lf %lf %lf %lf %lf", &a, &b, &c, &d, &e);
    double sum = a + b + c + d + e;
    printf("%.2lf", sum / 5.0);
    return 0;
}