#include <bits/stdc++.h>

using namespace std;

int main() {
	int n;
	while (cin >> n && n) {
		vector<int> s(n);
		int sum = 0;
		for (int i = 0; i < n; ++i) {
			cin >> s[i];
			sum += s[i];
		}
		auto m = 1.0*sum / n;
		auto sum2 = 0.0;
		for (auto si: s) {
			sum2 += (si-m)*(si-m);
		}
		auto var = sum2 / n;
		cout << fixed << setprecision(17) << sqrt(var) << '\n';
	}
}
