C++ :

#include<cstdio>
#include<math.h>
int main()
{
	long long int a,b,x,y,r;
	scanf("%lld %lld",&x,&y);
	a=x;
	b=y;
	if(y>x)
	{
		r=y;
		y=x;
		x=r;
	}
	r=x%y;
	while(r!=0)
	{
		x=y;
		y=r;
		r=x%y;
	}
	printf("yue:%lld",y);
}

Pascal :

var a,b,gys:longint;

function gcd(a,b:longint):longint;
begin
  if a mod b=0 then exit(b)
  else gcd:=gcd(b,a mod b);
end;

begin
  readln(a,b);
  gys:=gcd(a,b);
  writeln('yue:',gys);
end.