C :

#include <stdio.h> 
  int main()
  {
  	long long i,m=0,n;
  	scanf ("%lld",&n);
	for (i=0;n!=0;i++)
	{
		m=m*10+n%10;
		n/=10;
	}
	
	printf ("%lld",m);
  	return 0;
   } 

C++ :

#include <iostream>
#include <cstring>
using namespace std;
int main(){
	char s[20];
	gets(s);
	bool f=false;
	char t;
	int i;
	for(i=0;i<strlen(s)/2;i++){
		t=s[i];
		s[i]=s[strlen(s)-i-1];
		s[strlen(s)-i-1]=t;
	}
	for(i=0;i<strlen(s);i++){
		if(s[i]!='0'){
			f=true;
		}
		if(f==true){
			cout<<s[i];
		}
	}
}

Pascal :

program liumohan;
var n,s:string; m,i:longint;
begin
  read(n);
  for i:=length(n) downto 1 do
  s:=s+n[i];
  
  val(s,m);
  writeln(m);
  end.

Java :

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.nextLine();
		String temp = "";
		for(int i = s.length()-1;i >= 0;i--){
			temp += s.charAt(i);
		}
		int a = Integer.parseInt(temp);
		System.out.println(a);
	}
}

Python :

# 接收输入整数
n = int(input())
# 初始化求和
b = 0
# 逆序输出
while n > 0:
    b = b * 10 + n % 10
    n //= 10
print(b)