#include<stdio.h>
int main()
{
    int n,a,b,c;
    float read;
    scanf("%d",&n)
    scanf("%d %d %d",&a,&b,&c);
    read=(a+b+c)/n;
    if(n==0)
    {
        printf("No readings provided");
    }
    else
    {
        printf("%.3f",read);
    }
    return 0;
}