import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    double m, a2;
    while ((n = sc.nextInt()) != 0) {
      m = 0;
      a2 = 0;
      int s[] = new int[n];
      for (int i = 0; i < n; i++) {
        s[i] = sc.nextInt();
        m += s[i];
      }
      m /= n;
      for (int i = 0; i < n; i++) {
        a2 += (s[i] - m) * (s[i] - m);
      }
      a2 /= n;
      System.out.printf("%f\n", Math.sqrt(a2));
    }
  }
}
 import java.util.Scanner; Scanner java.util public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    double m, a2;
    while ((n = sc.nextInt()) != 0) {
      m = 0;
      a2 = 0;
      int s[] = new int[n];
      for (int i = 0; i < n; i++) {
        s[i] = sc.nextInt();
        m += s[i];
      }
      m /= n;
      for (int i = 0; i < n; i++) {
        a2 += (s[i] - m) * (s[i] - m);
      }
      a2 /= n;
      System.out.printf("%f\n", Math.sqrt(a2));
    }
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    double m, a2;
    while ((n = sc.nextInt()) != 0) {
      m = 0;
      a2 = 0;
      int s[] = new int[n];
      for (int i = 0; i < n; i++) {
        s[i] = sc.nextInt();
        m += s[i];
      }
      m /= n;
      for (int i = 0; i < n; i++) {
        a2 += (s[i] - m) * (s[i] - m);
      }
      a2 /= n;
      System.out.printf("%f\n", Math.sqrt(a2));
    }
  } main {
    Scanner sc = new Scanner(System.in);
    int n;
    double m, a2;
    while ((n = sc.nextInt()) != 0) {
      m = 0;
      a2 = 0;
      int s[] = new int[n];
      for (int i = 0; i < n; i++) {
        s[i] = sc.nextInt();
        m += s[i];
      }
      m /= n;
      for (int i = 0; i < n; i++) {
        a2 += (s[i] - m) * (s[i] - m);
      }
      a2 /= n;
      System.out.printf("%f\n", Math.sqrt(a2));
    }
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n; n double m m a2; a2 while ((n = sc.nextInt()) != 0) {
      m = 0;
      a2 = 0;
      int s[] = new int[n];
      for (int i = 0; i < n; i++) {
        s[i] = sc.nextInt();
        m += s[i];
      }
      m /= n;
      for (int i = 0; i < n; i++) {
        a2 += (s[i] - m) * (s[i] - m);
      }
      a2 /= n;
      System.out.printf("%f\n", Math.sqrt(a2));
    } (n = sc.nextInt()) != 0 (n = sc.nextInt()) n sc.nextInt() sc.nextInt sc 0 {
      m = 0;
      a2 = 0;
      int s[] = new int[n];
      for (int i = 0; i < n; i++) {
        s[i] = sc.nextInt();
        m += s[i];
      }
      m /= n;
      for (int i = 0; i < n; i++) {
        a2 += (s[i] - m) * (s[i] - m);
      }
      a2 /= n;
      System.out.printf("%f\n", Math.sqrt(a2));
    } m = 0 m 0 a2 = 0 a2 0 int s[] = new int[n]; s new int[n] n for (int i = 0; i < n; i++) {
        s[i] = sc.nextInt();
        m += s[i];
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        s[i] = sc.nextInt();
        m += s[i];
      } {
        s[i] = sc.nextInt();
        m += s[i];
      } s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc m += s[i] m s[i] s i m /= n m n for (int i = 0; i < n; i++) {
        a2 += (s[i] - m) * (s[i] - m);
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        a2 += (s[i] - m) * (s[i] - m);
      } {
        a2 += (s[i] - m) * (s[i] - m);
      } a2 += (s[i] - m) * (s[i] - m) a2 (s[i] - m) * (s[i] - m) (s[i] - m) s[i] s i m (s[i] - m) s[i] s i m a2 /= n a2 n System.out.printf("%f\n", Math.sqrt(a2)) System.out.printf System.out System System.out "%f\n" Math.sqrt(a2) Math.sqrt Math a2 String[] args args public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    double m, a2;
    while ((n = sc.nextInt()) != 0) {
      m = 0;
      a2 = 0;
      int s[] = new int[n];
      for (int i = 0; i < n; i++) {
        s[i] = sc.nextInt();
        m += s[i];
      }
      m /= n;
      for (int i = 0; i < n; i++) {
        a2 += (s[i] - m) * (s[i] - m);
      }
      a2 /= n;
      System.out.printf("%f\n", Math.sqrt(a2));
    }
  }
} public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    double m, a2;
    while ((n = sc.nextInt()) != 0) {
      m = 0;
      a2 = 0;
      int s[] = new int[n];
      for (int i = 0; i < n; i++) {
        s[i] = sc.nextInt();
        m += s[i];
      }
      m /= n;
      for (int i = 0; i < n; i++) {
        a2 += (s[i] - m) * (s[i] - m);
      }
      a2 /= n;
      System.out.printf("%f\n", Math.sqrt(a2));
    }
  }
} Main
import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    double m, a2;
    while ((n = sc.nextInt()) != 0) {
      m = 0;
      a2 = 0;
      int s[] = new int[n];
      for (int i = 0; i < n; i++) {
        s[i] = sc.nextInt();
        m += s[i];
      }
      m /= n;
      for (int i = 0; i < n; i++) {
        a2 += (s[i] - m) * (s[i] - m);
      }
      a2 /= n;
      System.out.printf("%f\n", Math.sqrt(a2));
    }
  }
}

