C :

#include<stdio.h>
int main()
{
	int a,b;
	scanf("%d",&a);
	printf("%d",a%10);
	printf("%d",(a%100)/10);
	printf("%d",(a%1000)/100);
	printf("%d\n",a/1000);
	return 0;
}

C++ :

#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;
int main()
  {int n,a,b,c,d;
   scanf("%d",&n);
   a=n%10;
   n=n/10;b=n%10;
   n=n/10;c=n%10;
   d=n/10;
   printf("%d%d%d%d",a,b,c,d);
   return 0;
  }

Pascal :

program aa;
var a,e,b,c,d,z:integer;
begin
 read(a);
 e:=(a mod 10);
 b:=(a mod 100-e)div 10;
 c:=(a mod 1000-e-b)div 100;
 d:=a div 1000;
 z:=e*1000+b*100+c*10+d;
 write(z);
end.

Java :

import java.util.Scanner;
public class Main
{
	private static Scanner in;

	public static void main (String[]args)
	{
		in = new Scanner(System.in);
		while(in.hasNextInt()){
			//System.out.println("请输入一个四位数：");
			int x=in.nextInt();
			int [] arr=new int[4];
			for(int n=0;n<4;n++) 
			{
				arr[n]=x%10;
				x=x/10;
			}
			//System.out.println(arr[0]*1000+arr[1]*100+arr[2]*10+arr[3]*1);
			for(int n=0;n<4;n++)
			{
				System.out.print(arr[n]);
			}
		} 
	}
}