Prinzessin from Pati

Program FPB;
uses wincrt;
var n,d : longint;
Begin
writeln(' PERHITUNGAN FAKTOR PERSEKUTUAN TERBESAR (FPB) ');
writeln;
write('Masukkan Bilangan Pertama (a) = ');readln(n);
writeln;
write('Masukkan Bilangan Kedua (b) = ');readln(d);
writeln;
Begin
while n<>d do
begin
if n>d then
n:=n-d
else
d:=d-n;
end;
end;
write('FPB = ',n or d);
end.