import java.util.Scanner;

public class Main {
	public static void main(String args[]) {
		int n, s[], i;
		double ave, a, ans;
		Scanner sc = new Scanner(System.in);
		while (true) {
			ave = 0.0;
			a = 0.0;
			n = sc.nextInt();
			if (n == 0) {
				break;
			}
			s = new int[n];
			for (i = 0; i < n; ++i) {
				s[i] = sc.nextInt();
				ave += s[i];
			}
			ave /= (double) n;
			for (i = 0; i < n; ++i) {
				a += (s[i] - ave) * (s[i] - ave);
			}
			a /= (double) n;
			ans = Math.sqrt(a);
			System.out.println(ans);
		}
		sc.close();
	}
}
 import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String args[]) {
		int n, s[], i;
		double ave, a, ans;
		Scanner sc = new Scanner(System.in);
		while (true) {
			ave = 0.0;
			a = 0.0;
			n = sc.nextInt();
			if (n == 0) {
				break;
			}
			s = new int[n];
			for (i = 0; i < n; ++i) {
				s[i] = sc.nextInt();
				ave += s[i];
			}
			ave /= (double) n;
			for (i = 0; i < n; ++i) {
				a += (s[i] - ave) * (s[i] - ave);
			}
			a /= (double) n;
			ans = Math.sqrt(a);
			System.out.println(ans);
		}
		sc.close();
	}
} Main public static void main(String args[]) {
		int n, s[], i;
		double ave, a, ans;
		Scanner sc = new Scanner(System.in);
		while (true) {
			ave = 0.0;
			a = 0.0;
			n = sc.nextInt();
			if (n == 0) {
				break;
			}
			s = new int[n];
			for (i = 0; i < n; ++i) {
				s[i] = sc.nextInt();
				ave += s[i];
			}
			ave /= (double) n;
			for (i = 0; i < n; ++i) {
				a += (s[i] - ave) * (s[i] - ave);
			}
			a /= (double) n;
			ans = Math.sqrt(a);
			System.out.println(ans);
		}
		sc.close();
	} main {
		int n, s[], i;
		double ave, a, ans;
		Scanner sc = new Scanner(System.in);
		while (true) {
			ave = 0.0;
			a = 0.0;
			n = sc.nextInt();
			if (n == 0) {
				break;
			}
			s = new int[n];
			for (i = 0; i < n; ++i) {
				s[i] = sc.nextInt();
				ave += s[i];
			}
			ave /= (double) n;
			for (i = 0; i < n; ++i) {
				a += (s[i] - ave) * (s[i] - ave);
			}
			a /= (double) n;
			ans = Math.sqrt(a);
			System.out.println(ans);
		}
		sc.close();
	} int n n s[] s i; i double ave ave a a ans; ans Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while (true) {
			ave = 0.0;
			a = 0.0;
			n = sc.nextInt();
			if (n == 0) {
				break;
			}
			s = new int[n];
			for (i = 0; i < n; ++i) {
				s[i] = sc.nextInt();
				ave += s[i];
			}
			ave /= (double) n;
			for (i = 0; i < n; ++i) {
				a += (s[i] - ave) * (s[i] - ave);
			}
			a /= (double) n;
			ans = Math.sqrt(a);
			System.out.println(ans);
		} true {
			ave = 0.0;
			a = 0.0;
			n = sc.nextInt();
			if (n == 0) {
				break;
			}
			s = new int[n];
			for (i = 0; i < n; ++i) {
				s[i] = sc.nextInt();
				ave += s[i];
			}
			ave /= (double) n;
			for (i = 0; i < n; ++i) {
				a += (s[i] - ave) * (s[i] - ave);
			}
			a /= (double) n;
			ans = Math.sqrt(a);
			System.out.println(ans);
		} ave = 0.0 ave 0.0 a = 0.0 a 0.0 n = sc.nextInt() n sc.nextInt() sc.nextInt sc if (n == 0) {
				break;
			} n == 0 n 0 {
				break;
			} break; s = new int[n] s new int[n] n for (i = 0; i < n; ++i) {
				s[i] = sc.nextInt();
				ave += s[i];
			} i = 0; i = 0 i 0 i < n i n ++i ++i i {
				s[i] = sc.nextInt();
				ave += s[i];
			} {
				s[i] = sc.nextInt();
				ave += s[i];
			} s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc ave += s[i] ave s[i] s i ave /= (double) n ave (double) n for (i = 0; i < n; ++i) {
				a += (s[i] - ave) * (s[i] - ave);
			} i = 0; i = 0 i 0 i < n i n ++i ++i i {
				a += (s[i] - ave) * (s[i] - ave);
			} {
				a += (s[i] - ave) * (s[i] - ave);
			} a += (s[i] - ave) * (s[i] - ave) a (s[i] - ave) * (s[i] - ave) (s[i] - ave) s[i] s i ave (s[i] - ave) s[i] s i ave a /= (double) n a (double) n ans = Math.sqrt(a) ans Math.sqrt(a) Math.sqrt Math a System.out.println(ans) System.out.println System.out System System.out ans sc.close() sc.close sc String args[] args public class Main {
	public static void main(String args[]) {
		int n, s[], i;
		double ave, a, ans;
		Scanner sc = new Scanner(System.in);
		while (true) {
			ave = 0.0;
			a = 0.0;
			n = sc.nextInt();
			if (n == 0) {
				break;
			}
			s = new int[n];
			for (i = 0; i < n; ++i) {
				s[i] = sc.nextInt();
				ave += s[i];
			}
			ave /= (double) n;
			for (i = 0; i < n; ++i) {
				a += (s[i] - ave) * (s[i] - ave);
			}
			a /= (double) n;
			ans = Math.sqrt(a);
			System.out.println(ans);
		}
		sc.close();
	}
} public class Main {
	public static void main(String args[]) {
		int n, s[], i;
		double ave, a, ans;
		Scanner sc = new Scanner(System.in);
		while (true) {
			ave = 0.0;
			a = 0.0;
			n = sc.nextInt();
			if (n == 0) {
				break;
			}
			s = new int[n];
			for (i = 0; i < n; ++i) {
				s[i] = sc.nextInt();
				ave += s[i];
			}
			ave /= (double) n;
			for (i = 0; i < n; ++i) {
				a += (s[i] - ave) * (s[i] - ave);
			}
			a /= (double) n;
			ans = Math.sqrt(a);
			System.out.println(ans);
		}
		sc.close();
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String args[]) {
		int n, s[], i;
		double ave, a, ans;
		Scanner sc = new Scanner(System.in);
		while (true) {
			ave = 0.0;
			a = 0.0;
			n = sc.nextInt();
			if (n == 0) {
				break;
			}
			s = new int[n];
			for (i = 0; i < n; ++i) {
				s[i] = sc.nextInt();
				ave += s[i];
			}
			ave /= (double) n;
			for (i = 0; i < n; ++i) {
				a += (s[i] - ave) * (s[i] - ave);
			}
			a /= (double) n;
			ans = Math.sqrt(a);
			System.out.println(ans);
		}
		sc.close();
	}
}

