#include <bits/stdc++.h>
using namespace std;

int main() {
  while (1) {
    int n;
    cin >> n;
    if (n == 0) break;
    int s[n];

    double sum = 0;
    for (int i = 0; i < n; i++) {
      cin >> s[i];
      sum += s[i];
    }
    double m = sum / n;
    double t = 0;
    for (int i = 0; i < n; i++) {
      t += (s[i]-m)*(s[i]-m);
    }
    double a = sqrt(t/n);

    cout << a << endl;
  }
      
}

