#include <cstdio>
#include <cmath>

const int LIM = 1e6;
int arr[LIM]; 

int main() {
	int n;
	while(scanf("%d", &n) == 1 && n) {
		int sum = 0;
		for(int i = 1; i <= n; i++) scanf("%d", &arr[i]), sum += arr[i];
		double avg = sum / (double)n, stddev = 0.0;
	//	printf("%lf\n", avg);
		for(int i = 1; i <= n; i++) stddev += pow(arr[i] - avg, 2.0);
		stddev /= n;
		printf("%.8lf\n", sqrt(stddev)); 
	}
	return 0;
}
