// Calcul detaille de PGCD(a,b)
a=input('a=')
b=input('b=')
    r=1;
     while r>0
       E=1;
         while E<=a/b
           E=E+1;
         end
       r=a-b*(E-1);
       a=b;
       b=r;
     end
  PGCD=a