#include<stdio.h>
int main(){
    int N,ind;
    float avg,sum;
    scanf("%d",&N);
    int marks[N];
    for(ind=0;ind<N;ind++){
        if(scanf("%d"&marks[ind])!=1||mark[ind]<0)
        {
            printf("Invalid input");
            return 0;
        }
        sum+=marks[ind];
    }
    avg=sum/N;
    printf("%.2f",avg);
    return 0;
}