#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv) {
    int n, sum=0, cases=0;
    while(1)
    {
        scanf("%d", &n);
        if (n==0)
            break;
        sum+=n;
        cases++;
    }

    printf("%.2f\n",(float)sum/cases);

    return 0;
}