import java.util.Scanner;

public class Main {
	public static Scanner sc;
	public static void main(String[] args) {
		sc=new Scanner(System.in);
		int n[]=new int[15];
		int score[][]=new int[15][1000];
		double ans[]=new double[1000];
		int i=0;
		int count=0;
		for(;;) {
			n[i]=sc.nextInt();
			if(n[i]==0) {
				break;
			}
			for(int j=0;j<n[i];j++) {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			}
			i++;
			count++;
		}
		//平均の取得
		double m[]=new double[15];
		int sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				sum+=score[i][j];
			}
			m[i]=(double)sum/n[i];
			//System.out.println(i+" "+m[i]);
			sum=0;
		}
		//標準偏差
		double Sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			}
			ans[i]=Math.sqrt((double)Sum/n[i]);
			//System.out.print(ans[i]);
			Sum=0;
		}
		for(i=0;i<count;i++) {
			System.out.printf("%.08f\n",ans[i]);
		}
	}
}
 import java.util.Scanner; Scanner java.util public class Main {
	public static Scanner sc;
	public static void main(String[] args) {
		sc=new Scanner(System.in);
		int n[]=new int[15];
		int score[][]=new int[15][1000];
		double ans[]=new double[1000];
		int i=0;
		int count=0;
		for(;;) {
			n[i]=sc.nextInt();
			if(n[i]==0) {
				break;
			}
			for(int j=0;j<n[i];j++) {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			}
			i++;
			count++;
		}
		//平均の取得
		double m[]=new double[15];
		int sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				sum+=score[i][j];
			}
			m[i]=(double)sum/n[i];
			//System.out.println(i+" "+m[i]);
			sum=0;
		}
		//標準偏差
		double Sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			}
			ans[i]=Math.sqrt((double)Sum/n[i]);
			//System.out.print(ans[i]);
			Sum=0;
		}
		for(i=0;i<count;i++) {
			System.out.printf("%.08f\n",ans[i]);
		}
	}
} Main public static Scanner sc; sc public static void main(String[] args) {
		sc=new Scanner(System.in);
		int n[]=new int[15];
		int score[][]=new int[15][1000];
		double ans[]=new double[1000];
		int i=0;
		int count=0;
		for(;;) {
			n[i]=sc.nextInt();
			if(n[i]==0) {
				break;
			}
			for(int j=0;j<n[i];j++) {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			}
			i++;
			count++;
		}
		//平均の取得
		double m[]=new double[15];
		int sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				sum+=score[i][j];
			}
			m[i]=(double)sum/n[i];
			//System.out.println(i+" "+m[i]);
			sum=0;
		}
		//標準偏差
		double Sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			}
			ans[i]=Math.sqrt((double)Sum/n[i]);
			//System.out.print(ans[i]);
			Sum=0;
		}
		for(i=0;i<count;i++) {
			System.out.printf("%.08f\n",ans[i]);
		}
	} main {
		sc=new Scanner(System.in);
		int n[]=new int[15];
		int score[][]=new int[15][1000];
		double ans[]=new double[1000];
		int i=0;
		int count=0;
		for(;;) {
			n[i]=sc.nextInt();
			if(n[i]==0) {
				break;
			}
			for(int j=0;j<n[i];j++) {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			}
			i++;
			count++;
		}
		//平均の取得
		double m[]=new double[15];
		int sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				sum+=score[i][j];
			}
			m[i]=(double)sum/n[i];
			//System.out.println(i+" "+m[i]);
			sum=0;
		}
		//標準偏差
		double Sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			}
			ans[i]=Math.sqrt((double)Sum/n[i]);
			//System.out.print(ans[i]);
			Sum=0;
		}
		for(i=0;i<count;i++) {
			System.out.printf("%.08f\n",ans[i]);
		}
	} sc=new Scanner(System.in) sc new Scanner(System.in) int n[]=new int[15]; n new int[15] 15 int score[][]=new int[15][1000]; score new int[15][1000] 15 1000 double ans[]=new double[1000]; ans new double[1000] 1000 int i=0; i 0 int count=0; count 0 for(;;) {
			n[i]=sc.nextInt();
			if(n[i]==0) {
				break;
			}
			for(int j=0;j<n[i];j++) {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			}
			i++;
			count++;
		} ; {
			n[i]=sc.nextInt();
			if(n[i]==0) {
				break;
			}
			for(int j=0;j<n[i];j++) {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			}
			i++;
			count++;
		} {
			n[i]=sc.nextInt();
			if(n[i]==0) {
				break;
			}
			for(int j=0;j<n[i];j++) {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			}
			i++;
			count++;
		} n[i]=sc.nextInt() n[i] n i sc.nextInt() sc.nextInt sc if(n[i]==0) {
				break;
			} n[i]==0 n[i] n i 0 {
				break;
			} break; for(int j=0;j<n[i];j++) {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			} int j=0; int j=0; j 0 j<n[i] j n[i] n i j++ j++ j {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			} {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			} score[i][j]=sc.nextInt() score[i][j] score[i] score i j sc.nextInt() sc.nextInt sc i++ i count++ count double m[]=new double[15]; m new double[15] 15 int sum=0; sum 0 for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				sum+=score[i][j];
			}
			m[i]=(double)sum/n[i];
			//System.out.println(i+" "+m[i]);
			sum=0;
		} i=0; i=0 i 0 i<count i count i++ i++ i {
			for(int j=0;j<n[i];j++) {
				sum+=score[i][j];
			}
			m[i]=(double)sum/n[i];
			//System.out.println(i+" "+m[i]);
			sum=0;
		} {
			for(int j=0;j<n[i];j++) {
				sum+=score[i][j];
			}
			m[i]=(double)sum/n[i];
			//System.out.println(i+" "+m[i]);
			sum=0;
		} for(int j=0;j<n[i];j++) {
				sum+=score[i][j];
			} int j=0; int j=0; j 0 j<n[i] j n[i] n i j++ j++ j {
				sum+=score[i][j];
			} {
				sum+=score[i][j];
			} sum+=score[i][j] sum score[i][j] score[i] score i j m[i]=(double)sum/n[i] m[i] m i (double)sum/n[i] (double)sum n[i] n i sum=0 sum 0 double Sum=0; Sum 0 for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			}
			ans[i]=Math.sqrt((double)Sum/n[i]);
			//System.out.print(ans[i]);
			Sum=0;
		} i=0; i=0 i 0 i<count i count i++ i++ i {
			for(int j=0;j<n[i];j++) {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			}
			ans[i]=Math.sqrt((double)Sum/n[i]);
			//System.out.print(ans[i]);
			Sum=0;
		} {
			for(int j=0;j<n[i];j++) {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			}
			ans[i]=Math.sqrt((double)Sum/n[i]);
			//System.out.print(ans[i]);
			Sum=0;
		} for(int j=0;j<n[i];j++) {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			} int j=0; int j=0; j 0 j<n[i] j n[i] n i j++ j++ j {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			} {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			} Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]) Sum (double)(score[i][j]-m[i])*(score[i][j]-m[i]) (double)(score[i][j]-m[i]) score[i][j] score[i] score i j m[i] m i (score[i][j]-m[i]) score[i][j] score[i] score i j m[i] m i ans[i]=Math.sqrt((double)Sum/n[i]) ans[i] ans i Math.sqrt((double)Sum/n[i]) Math.sqrt Math (double)Sum/n[i] (double)Sum n[i] n i Sum=0 Sum 0 for(i=0;i<count;i++) {
			System.out.printf("%.08f\n",ans[i]);
		} i=0; i=0 i 0 i<count i count i++ i++ i {
			System.out.printf("%.08f\n",ans[i]);
		} {
			System.out.printf("%.08f\n",ans[i]);
		} System.out.printf("%.08f\n",ans[i]) System.out.printf System.out System System.out "%.08f\n" ans[i] ans i String[] args args public class Main {
	public static Scanner sc;
	public static void main(String[] args) {
		sc=new Scanner(System.in);
		int n[]=new int[15];
		int score[][]=new int[15][1000];
		double ans[]=new double[1000];
		int i=0;
		int count=0;
		for(;;) {
			n[i]=sc.nextInt();
			if(n[i]==0) {
				break;
			}
			for(int j=0;j<n[i];j++) {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			}
			i++;
			count++;
		}
		//平均の取得
		double m[]=new double[15];
		int sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				sum+=score[i][j];
			}
			m[i]=(double)sum/n[i];
			//System.out.println(i+" "+m[i]);
			sum=0;
		}
		//標準偏差
		double Sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			}
			ans[i]=Math.sqrt((double)Sum/n[i]);
			//System.out.print(ans[i]);
			Sum=0;
		}
		for(i=0;i<count;i++) {
			System.out.printf("%.08f\n",ans[i]);
		}
	}
} public class Main {
	public static Scanner sc;
	public static void main(String[] args) {
		sc=new Scanner(System.in);
		int n[]=new int[15];
		int score[][]=new int[15][1000];
		double ans[]=new double[1000];
		int i=0;
		int count=0;
		for(;;) {
			n[i]=sc.nextInt();
			if(n[i]==0) {
				break;
			}
			for(int j=0;j<n[i];j++) {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			}
			i++;
			count++;
		}
		//平均の取得
		double m[]=new double[15];
		int sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				sum+=score[i][j];
			}
			m[i]=(double)sum/n[i];
			//System.out.println(i+" "+m[i]);
			sum=0;
		}
		//標準偏差
		double Sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			}
			ans[i]=Math.sqrt((double)Sum/n[i]);
			//System.out.print(ans[i]);
			Sum=0;
		}
		for(i=0;i<count;i++) {
			System.out.printf("%.08f\n",ans[i]);
		}
	}
} Main
import java.util.Scanner;

public class Main {
	public static Scanner sc;
	public static void main(String[] args) {
		sc=new Scanner(System.in);
		int n[]=new int[15];
		int score[][]=new int[15][1000];
		double ans[]=new double[1000];
		int i=0;
		int count=0;
		for(;;) {
			n[i]=sc.nextInt();
			if(n[i]==0) {
				break;
			}
			for(int j=0;j<n[i];j++) {
				score[i][j]=sc.nextInt();
				//System.out.print(i+" "+j+"="+score[i][j]+"\n");
			}
			i++;
			count++;
		}
		//平均の取得
		double m[]=new double[15];
		int sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				sum+=score[i][j];
			}
			m[i]=(double)sum/n[i];
			//System.out.println(i+" "+m[i]);
			sum=0;
		}
		//標準偏差
		double Sum=0;
		for(i=0;i<count;i++) {
			for(int j=0;j<n[i];j++) {
				Sum+=(double)(score[i][j]-m[i])*(score[i][j]-m[i]);
				//System.out.print(i+" "+j+":"+Sum+"\n");
			}
			ans[i]=Math.sqrt((double)Sum/n[i]);
			//System.out.print(ans[i]);
			Sum=0;
		}
		for(i=0;i<count;i++) {
			System.out.printf("%.08f\n",ans[i]);
		}
	}
}

