#include <iostream>

using namespace std;

int main()
{
        int a,b,r,a0,b0;
                
        cout << "Ce programme détermine le PGCD de 2 entiers saisis" << endl;
        
        do
        {
                cout << "Veuillez saisir deux entier a et b tel que a < b : " ;
                cin >> a >> b;
        } while ((a<=0) || (b<=a));
        
        a0 = a;
        b0 = b;
        
        r = b mod a; 
        
        while (r!=0)
        {
                b = a;
                a = r;
                r = b mod a; 
        }
        
        cout << "le PGCD de " << a0 << " et " << b0 << " est " << a << endl;
}