C :

#include <stdio.h>
int main ()
{int p,r,n,m,temp;

 scanf("%d %d",&n,&m);
 if (n<m)              
     {temp=n;
      n=m;
      m=temp;                //把大数放在n中, 小数放在m中
     }
 p=n*m;                     //先将n和m的乘积保存在p中, 以便求最小公倍数时用
 while (m!=0)               //求n和m的最大公约数
    {r=n%m;
     n=m;
     m=r;
 }
 printf("%d",n);
 
 return 0;
 } 

C++ :

#include <iostream>
#include <iomanip>

using namespace std;

int main(){
    int a,b,i;
    cin>>b>>a;
    for(i=a;i>=1;i--){
    	if(a%i==0&&b%i==0){
    		cout<<i<<endl;
    		break;
		}
	}
}

Pascal :

var a,b:longint;
function gys(x,y:longint):longint;
var k:longint;
begin
  k:=0;
  k:=x mod y;
  while k<>0 do
   begin
    x:=y;
    y:=k;
    k:=x mod y;
   end;
  gys:=y;
end;
begin
  read(a,b);
  writeln(gys(a,b));
end.

Java :

import java.util.Scanner;
public class Main{
	public static void main(String[] args) {
		String str=new Scanner(System.in).nextLine();
		String[] strArray=str.split(" ");
		int M=Integer.valueOf(strArray[0]);
		int N=Integer.valueOf(strArray[1]);
		int a=0;
		for(int i=1;i<=M&&i<=N;i++){
			if(M%i==0&&N%i==0){
				 a=i;
			}
		}
		System.out.println(a);
	}
}

Python :

a, b = map(int, input().split())
if a < b:
    a, b = b, a;
x = a % b;
while x != 0:
    a = b
    b = x
    x = a % b
    print(b)