program nguyen_to_cung_nhau;
uses crt;
var a,b:longint;
function ucln(a,b:longint):longint;
begin
while a<>b do
if a>b then
a:=a-b else
b:=b-a;
if a=b then
ucln:=a;
end;
begin
clrscr;
write('nhap a=');readln(a);
write('nhap b=');readln(b);
if ucln(a,b)=1 then
writeln('la 2 so nguyen to cung nhau')
else writeln('ko la 2 so nguyen to cung nhau');
readln
end.