Lời giải:

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.