#include <stdio.h>
#include <cmath>
using namespace std;
int main(){
  int i, n;
  while (scanf("%d", &n)) {
    int sum=0, arr[n];
    double avg, s1=0.0, s2;
    if (n==0) break;
    for (i=0; i<n; i++) {
      scanf("%d", &arr[i]);
      sum+=arr[i];
    }
    avg=(double)(sum)/n;
    for (i=0; i<n; i++) {
      s1+=(arr[i]-avg)*(arr[i]-avg);
    }
    s2=s1/n;
    printf("%lf\n", sqrt(s2));
  }
}
