#include <iostream>
#include <math.h>

using namespace std;

void nhap(int &a, int &b) {
	do {
		cout<<"Nhap so nguyen duong a: "; cin>>a;
		cout<<"Nhap so nguyen duong b: "; cin>>b;
		if (a <= 0 || b <= 0) cout<<"Vui long nhap lai"<<endl; 
	} while (a <= 0 || b <= 0);
}

int ucln(int a, int b) {
	int tmp, r;
	if (a < b) {
		tmp = a;
		a = b;
		b = tmp;
	}
	r = a % b;
	while (r != 0) {
		a = b;
		b = r;
		r = a % b;
	};
	return b;
	/*
	int r;
	while (b > 0) {
		r = a % b;
		a = b;
		b = r;
	}
	return a;
	*/
}

int main() {
	int a, b;
	nhap(a, b);
	cout<<"Tim duoc UCLN cua "<<a<<" va "<<b<<" la "<<ucln(a, b);
	return 0;
}