#include<stdio.h>
vold calculate_average(int count,int readings[]) {
    if(count == 0) {
        print("no readings provided");
        return;
    }
    int sum = 0;
    for(int i = 0; i < count;i++) {
        sum += readings[i];
    }
    double average = (double)sum / count;
    printf("%.2f",average);
}
int main() {
    int n;
    if(scanf("%d,&n") != 1) {
        return 1;
    }
    if(n < 0 || n > 100) {
        return 1;
    }
    int reading[n];
    for (int i = 0;i < n;i++) {
        if(scanf("%d",&reading[i]) != 1) {
            return 1;
        }
    }
    calculate_average(n,reading);
    return 0;
}