Program PGCD_Diff;
Var a, b : Integer;
Begin
Repeat
Writeln ('Saisir deux entiers >0 ');
Readln (a, b);
Until(a>0) and (b>0);
While a<>b Do
If a>b Then a:= a-b
Else b:= b-a ;
Writeln ('PGCD =', a);
End.