C :

#include <stdio.h>
 
int main()
 
{
    int a;
float b;
    while(scanf("%d",&a) != EOF)
 {
 if (a==1) 
   b=28.0/45;
  else if(a==2)
    b=1.0/45;
    else if(a==3)
    b=16.0/45;
    else if(a==4)
    b=1.0/5;
  else if (a==0)
		b=0.0001;
        printf("%.4f\n",b);
		
}
    return 0;
}

C++ :

#include <stdio.h>
 
int main()
 
{
    int a;
    float b;
    while(scanf("%d",&a) != EOF)
 {if (a==1) 
    b=28.0/45; //将“作业答案”替换为该题答案。若有多行，用多行重复输出。
  else if (a==2)
    b=1.0/45;
  else if(a==3)
    b=16.0/45;
  else if(a==4)
    b=1.0/5;
  else 
	b=0.0001;
        printf("%.4f\n",b);
}
    return 0;
}

Java :

import java.text.DecimalFormat;
import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		
		float f[] = new float[2];
		Scanner reader = new Scanner(System.in); 
		int a;
		DecimalFormat df=new DecimalFormat("#0.0000");
		while(reader.hasNext()){
			a = reader.nextInt();
			switch(a){
			case 1:f = null;
		                             f =new float[1];
		                             f[0]=(float)28/45;
			           break;
			case 2:f = null;
			       f =new float[1];
			       f[0]=(float)1/45;
			       break;
			case 3:f = null;
		                             f =new float[1];
		                            f[0]=(float)16/45;
		                               break;
			case 4:f = null;
		                              f =new float[1];
		                              f[0]=(float)1/5;
		                              break;
		               default:  f = null;
                                                                f =new float[1];
                                                                f[0]=(float)0.0001;
                                                               break;
			}
			for(int i=0;i<f.length;i++){
				
				System.out.println(df.format(f[i]));
			}
		}
	}
}