uses crt;
var a, b, x, y, sd, UC: integer;
begin
clrscr;
write ('nhap a: '); readln (a);
write ('nhap b: '); readln (b);
x:=a;
y:=b;
while (b<>0) do
begin
sd:=a mod b;
a:=b;
b:=sd;
end;
writeln;
UC:=a;
writeln ('ucln cua ',x,' va ',y,' la: ',UC);
readln;
end.