#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <string>
#include <cmath>
#include<math.h>

using namespace std;

int main() {
	int n;
	cin >> n;
	while (n!=0) {
		double s[1000] = {}, sum = 0,a = 0;
		for (int i = 0; i < n; i++) {
			cin >> s[i];
			sum += s[i];
		}
		for (int i = 0; i < n; i++)a += (s[i] - sum/n) * (s[i] - sum/n)/n;
		printf("%.8lf\n", sqrt(a));
		cin >> n;
	}
}
