Pascal :

var
 m,n,a,b,r:integer;
begin
 readln(m,n);
 a:=m;b:=n; r:=a mod b;
 while  r<>0 do
 begin
  a:=b;
  b:=r;
  r:=a mod b;
 end;
 write(abs(b));
end.

Java :

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		Scanner input=new Scanner(System.in);
		int n1=input.nextInt();
		int n2=input.nextInt();
		int d=0;
		
		if(n1<n2){
			d=n1;
		}
		else{
			d=n2;
		}
		
		while(n1%d!=0 || n2%d!=0){
			d=d-1;
		}
		
		System.out.print(d);
		
	}

}