// editor5
#include<stdio.h>
int main(){
    int n,temp,sum=0;
    if(scanf("%d,&n"!=1||n<1)){
        printf("No readings provided\n");
        return 0;
    }
    for(int i=0;i<n;i++){
        scanf("%d",&temp);
        sum +=temp;
    }
    float average=(float)sum/n;
    printf("%.2f\n",average);
    return 0;
}