import java.io.*;

class Main {
	public static void main(String[] args) {
		BufferedReader kb = new BufferedReader( new InputStreamReader( System.in ) );
		try {
			int n;
			String str;
			double[] s = new double[ 1000+1 ];
			int i;
			double ave = 0, sum = 0, a = 0;
			while( true ) {
				n = Integer.parseInt( kb.readLine() );
				if( 0 == n ) { break; }
				sum = i = 0;
				for( String nums: kb.readLine().split( " ", 0 ) ) {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				}
				ave = sum/n;
				sum = 0;
				for( i=0; i<n; i++ ) {
					sum += Math.pow( s[i]-ave, 2 );
				}
				a = Math.sqrt( sum/n );
				System.out.print( a + "\n" );
			}
			
			
		} catch( IOException e ) {
			System.err.println( e );
		}
	}
} import java.io.*; io.* java class Main {
	public static void main(String[] args) {
		BufferedReader kb = new BufferedReader( new InputStreamReader( System.in ) );
		try {
			int n;
			String str;
			double[] s = new double[ 1000+1 ];
			int i;
			double ave = 0, sum = 0, a = 0;
			while( true ) {
				n = Integer.parseInt( kb.readLine() );
				if( 0 == n ) { break; }
				sum = i = 0;
				for( String nums: kb.readLine().split( " ", 0 ) ) {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				}
				ave = sum/n;
				sum = 0;
				for( i=0; i<n; i++ ) {
					sum += Math.pow( s[i]-ave, 2 );
				}
				a = Math.sqrt( sum/n );
				System.out.print( a + "\n" );
			}
			
			
		} catch( IOException e ) {
			System.err.println( e );
		}
	}
} Main public static void main(String[] args) {
		BufferedReader kb = new BufferedReader( new InputStreamReader( System.in ) );
		try {
			int n;
			String str;
			double[] s = new double[ 1000+1 ];
			int i;
			double ave = 0, sum = 0, a = 0;
			while( true ) {
				n = Integer.parseInt( kb.readLine() );
				if( 0 == n ) { break; }
				sum = i = 0;
				for( String nums: kb.readLine().split( " ", 0 ) ) {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				}
				ave = sum/n;
				sum = 0;
				for( i=0; i<n; i++ ) {
					sum += Math.pow( s[i]-ave, 2 );
				}
				a = Math.sqrt( sum/n );
				System.out.print( a + "\n" );
			}
			
			
		} catch( IOException e ) {
			System.err.println( e );
		}
	} main {
		BufferedReader kb = new BufferedReader( new InputStreamReader( System.in ) );
		try {
			int n;
			String str;
			double[] s = new double[ 1000+1 ];
			int i;
			double ave = 0, sum = 0, a = 0;
			while( true ) {
				n = Integer.parseInt( kb.readLine() );
				if( 0 == n ) { break; }
				sum = i = 0;
				for( String nums: kb.readLine().split( " ", 0 ) ) {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				}
				ave = sum/n;
				sum = 0;
				for( i=0; i<n; i++ ) {
					sum += Math.pow( s[i]-ave, 2 );
				}
				a = Math.sqrt( sum/n );
				System.out.print( a + "\n" );
			}
			
			
		} catch( IOException e ) {
			System.err.println( e );
		}
	} BufferedReader kb = new BufferedReader( new InputStreamReader( System.in ) ); kb new BufferedReader( new InputStreamReader( System.in ) ) try {
			int n;
			String str;
			double[] s = new double[ 1000+1 ];
			int i;
			double ave = 0, sum = 0, a = 0;
			while( true ) {
				n = Integer.parseInt( kb.readLine() );
				if( 0 == n ) { break; }
				sum = i = 0;
				for( String nums: kb.readLine().split( " ", 0 ) ) {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				}
				ave = sum/n;
				sum = 0;
				for( i=0; i<n; i++ ) {
					sum += Math.pow( s[i]-ave, 2 );
				}
				a = Math.sqrt( sum/n );
				System.out.print( a + "\n" );
			}
			
			
		} catch( IOException e ) {
			System.err.println( e );
		} catch( IOException e ) {
			System.err.println( e );
		} IOException e {
			System.err.println( e );
		} System.err.println( e ) System.err.println System.err System System.err e {
			int n;
			String str;
			double[] s = new double[ 1000+1 ];
			int i;
			double ave = 0, sum = 0, a = 0;
			while( true ) {
				n = Integer.parseInt( kb.readLine() );
				if( 0 == n ) { break; }
				sum = i = 0;
				for( String nums: kb.readLine().split( " ", 0 ) ) {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				}
				ave = sum/n;
				sum = 0;
				for( i=0; i<n; i++ ) {
					sum += Math.pow( s[i]-ave, 2 );
				}
				a = Math.sqrt( sum/n );
				System.out.print( a + "\n" );
			}
			
			
		} int n; n String str; str double[] s = new double[ 1000+1 ]; s new double[ 1000+1 ] 1000+1 1000 1 int i; i double ave = 0 ave 0 sum = 0 sum 0 a = 0; a 0 while( true ) {
				n = Integer.parseInt( kb.readLine() );
				if( 0 == n ) { break; }
				sum = i = 0;
				for( String nums: kb.readLine().split( " ", 0 ) ) {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				}
				ave = sum/n;
				sum = 0;
				for( i=0; i<n; i++ ) {
					sum += Math.pow( s[i]-ave, 2 );
				}
				a = Math.sqrt( sum/n );
				System.out.print( a + "\n" );
			} true {
				n = Integer.parseInt( kb.readLine() );
				if( 0 == n ) { break; }
				sum = i = 0;
				for( String nums: kb.readLine().split( " ", 0 ) ) {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				}
				ave = sum/n;
				sum = 0;
				for( i=0; i<n; i++ ) {
					sum += Math.pow( s[i]-ave, 2 );
				}
				a = Math.sqrt( sum/n );
				System.out.print( a + "\n" );
			} n = Integer.parseInt( kb.readLine() ) n Integer.parseInt( kb.readLine() ) Integer.parseInt Integer kb.readLine() kb.readLine kb if( 0 == n ) { break; } 0 == n 0 n { break; } break; sum = i = 0 sum i = 0 i 0 for( String nums: kb.readLine().split( " ", 0 ) ) {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				} String nums kb.readLine().split( " ", 0 ) kb.readLine().split kb.readLine() kb.readLine kb " " 0 {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				} {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				} s[i] = Double.parseDouble( nums ) s[i] s i Double.parseDouble( nums ) Double.parseDouble Double nums sum += s[i++] sum s[i++] s i++ i ave = sum/n ave sum/n sum n sum = 0 sum 0 for( i=0; i<n; i++ ) {
					sum += Math.pow( s[i]-ave, 2 );
				} i=0; i=0 i 0 i<n i n i++ i++ i {
					sum += Math.pow( s[i]-ave, 2 );
				} {
					sum += Math.pow( s[i]-ave, 2 );
				} sum += Math.pow( s[i]-ave, 2 ) sum Math.pow( s[i]-ave, 2 ) Math.pow Math s[i]-ave s[i] s i ave 2 a = Math.sqrt( sum/n ) a Math.sqrt( sum/n ) Math.sqrt Math sum/n sum n System.out.print( a + "\n" ) System.out.print System.out System System.out a + "\n" a "\n" String[] args args
import java.io.*;

class Main {
	public static void main(String[] args) {
		BufferedReader kb = new BufferedReader( new InputStreamReader( System.in ) );
		try {
			int n;
			String str;
			double[] s = new double[ 1000+1 ];
			int i;
			double ave = 0, sum = 0, a = 0;
			while( true ) {
				n = Integer.parseInt( kb.readLine() );
				if( 0 == n ) { break; }
				sum = i = 0;
				for( String nums: kb.readLine().split( " ", 0 ) ) {
					s[i] = Double.parseDouble( nums );
					sum += s[i++];
				}
				ave = sum/n;
				sum = 0;
				for( i=0; i<n; i++ ) {
					sum += Math.pow( s[i]-ave, 2 );
				}
				a = Math.sqrt( sum/n );
				System.out.print( a + "\n" );
			}
			
			
		} catch( IOException e ) {
			System.err.println( e );
		}
	}
}