import java.util.Scanner;

public class Main 
{
	public static void main(String[] args)
	{
		Scanner scanner = new Scanner(System.in);
		
		for(;;)
		{
			int n = scanner.nextInt();
			if(n == 0)
			{
				break;
			}
			
			double[] s = new double[1000];
			double sum = 0;
			for(int i=0; i<n; i++)
			{
				s[i] = scanner.nextDouble();
				sum += s[i];
			}
			
			double m = sum/n;
			double v = 0;
			for(int i=0; i<n; i++)
			{
				v += (s[i] - m) * (s[i] - m);
			}

			System.out.printf("%1$.8f\n", Math.sqrt(v/n));
		}
	}
} import java.util.Scanner; Scanner java.util public class Main 
{
	public static void main(String[] args)
	{
		Scanner scanner = new Scanner(System.in);
		
		for(;;)
		{
			int n = scanner.nextInt();
			if(n == 0)
			{
				break;
			}
			
			double[] s = new double[1000];
			double sum = 0;
			for(int i=0; i<n; i++)
			{
				s[i] = scanner.nextDouble();
				sum += s[i];
			}
			
			double m = sum/n;
			double v = 0;
			for(int i=0; i<n; i++)
			{
				v += (s[i] - m) * (s[i] - m);
			}

			System.out.printf("%1$.8f\n", Math.sqrt(v/n));
		}
	}
} Main public static void main(String[] args)
	{
		Scanner scanner = new Scanner(System.in);
		
		for(;;)
		{
			int n = scanner.nextInt();
			if(n == 0)
			{
				break;
			}
			
			double[] s = new double[1000];
			double sum = 0;
			for(int i=0; i<n; i++)
			{
				s[i] = scanner.nextDouble();
				sum += s[i];
			}
			
			double m = sum/n;
			double v = 0;
			for(int i=0; i<n; i++)
			{
				v += (s[i] - m) * (s[i] - m);
			}

			System.out.printf("%1$.8f\n", Math.sqrt(v/n));
		}
	} main {
		Scanner scanner = new Scanner(System.in);
		
		for(;;)
		{
			int n = scanner.nextInt();
			if(n == 0)
			{
				break;
			}
			
			double[] s = new double[1000];
			double sum = 0;
			for(int i=0; i<n; i++)
			{
				s[i] = scanner.nextDouble();
				sum += s[i];
			}
			
			double m = sum/n;
			double v = 0;
			for(int i=0; i<n; i++)
			{
				v += (s[i] - m) * (s[i] - m);
			}

			System.out.printf("%1$.8f\n", Math.sqrt(v/n));
		}
	} Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) for(;;)
		{
			int n = scanner.nextInt();
			if(n == 0)
			{
				break;
			}
			
			double[] s = new double[1000];
			double sum = 0;
			for(int i=0; i<n; i++)
			{
				s[i] = scanner.nextDouble();
				sum += s[i];
			}
			
			double m = sum/n;
			double v = 0;
			for(int i=0; i<n; i++)
			{
				v += (s[i] - m) * (s[i] - m);
			}

			System.out.printf("%1$.8f\n", Math.sqrt(v/n));
		} ; {
			int n = scanner.nextInt();
			if(n == 0)
			{
				break;
			}
			
			double[] s = new double[1000];
			double sum = 0;
			for(int i=0; i<n; i++)
			{
				s[i] = scanner.nextDouble();
				sum += s[i];
			}
			
			double m = sum/n;
			double v = 0;
			for(int i=0; i<n; i++)
			{
				v += (s[i] - m) * (s[i] - m);
			}

			System.out.printf("%1$.8f\n", Math.sqrt(v/n));
		} {
			int n = scanner.nextInt();
			if(n == 0)
			{
				break;
			}
			
			double[] s = new double[1000];
			double sum = 0;
			for(int i=0; i<n; i++)
			{
				s[i] = scanner.nextDouble();
				sum += s[i];
			}
			
			double m = sum/n;
			double v = 0;
			for(int i=0; i<n; i++)
			{
				v += (s[i] - m) * (s[i] - m);
			}

			System.out.printf("%1$.8f\n", Math.sqrt(v/n));
		} int n = scanner.nextInt(); n scanner.nextInt() scanner.nextInt scanner if(n == 0)
			{
				break;
			} n == 0 n 0 {
				break;
			} break; double[] s = new double[1000]; s new double[1000] 1000 double sum = 0; sum 0 for(int i=0; i<n; i++)
			{
				s[i] = scanner.nextDouble();
				sum += s[i];
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				s[i] = scanner.nextDouble();
				sum += s[i];
			} {
				s[i] = scanner.nextDouble();
				sum += s[i];
			} s[i] = scanner.nextDouble() s[i] s i scanner.nextDouble() scanner.nextDouble scanner sum += s[i] sum s[i] s i double m = sum/n; m sum/n sum n double v = 0; v 0 for(int i=0; i<n; i++)
			{
				v += (s[i] - m) * (s[i] - m);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				v += (s[i] - m) * (s[i] - m);
			} {
				v += (s[i] - m) * (s[i] - m);
			} v += (s[i] - m) * (s[i] - m) v (s[i] - m) * (s[i] - m) (s[i] - m) s[i] s i m (s[i] - m) s[i] s i m System.out.printf("%1$.8f\n", Math.sqrt(v/n)) System.out.printf System.out System System.out "%1$.8f\n" Math.sqrt(v/n) Math.sqrt Math v/n v n String[] args args public class Main 
{
	public static void main(String[] args)
	{
		Scanner scanner = new Scanner(System.in);
		
		for(;;)
		{
			int n = scanner.nextInt();
			if(n == 0)
			{
				break;
			}
			
			double[] s = new double[1000];
			double sum = 0;
			for(int i=0; i<n; i++)
			{
				s[i] = scanner.nextDouble();
				sum += s[i];
			}
			
			double m = sum/n;
			double v = 0;
			for(int i=0; i<n; i++)
			{
				v += (s[i] - m) * (s[i] - m);
			}

			System.out.printf("%1$.8f\n", Math.sqrt(v/n));
		}
	}
} public class Main 
{
	public static void main(String[] args)
	{
		Scanner scanner = new Scanner(System.in);
		
		for(;;)
		{
			int n = scanner.nextInt();
			if(n == 0)
			{
				break;
			}
			
			double[] s = new double[1000];
			double sum = 0;
			for(int i=0; i<n; i++)
			{
				s[i] = scanner.nextDouble();
				sum += s[i];
			}
			
			double m = sum/n;
			double v = 0;
			for(int i=0; i<n; i++)
			{
				v += (s[i] - m) * (s[i] - m);
			}

			System.out.printf("%1$.8f\n", Math.sqrt(v/n));
		}
	}
} Main
import java.util.Scanner;

public class Main 
{
	public static void main(String[] args)
	{
		Scanner scanner = new Scanner(System.in);
		
		for(;;)
		{
			int n = scanner.nextInt();
			if(n == 0)
			{
				break;
			}
			
			double[] s = new double[1000];
			double sum = 0;
			for(int i=0; i<n; i++)
			{
				s[i] = scanner.nextDouble();
				sum += s[i];
			}
			
			double m = sum/n;
			double v = 0;
			for(int i=0; i<n; i++)
			{
				v += (s[i] - m) * (s[i] - m);
			}

			System.out.printf("%1$.8f\n", Math.sqrt(v/n));
		}
	}
}