#include <cmath>
#include <iostream>
#include <vector>

int main() {
  int n;
  while (std::cin >> n) {
    if (n == 0)
      break;
    std::vector<int> score(n, 0);
    double m = 0;
    for (int i = 0; i < n; i++) {
      std::cin >> score[i];
      m += score[i];
    }
    m /= n;
    double v=0;
    for (auto s : score) {
      v += pow(s - m, 2);
    }
    std::cout << sqrt(v / n) << std::endl;
  }
}

