progra kiemtra;
uses crt;
var a,i:integer;
kt:boolean;
begin
clrscr;
write('Nhap a: '); readln(a);
kt:=true;
for i:=2 to trunc(sqrt(a)) do
if a mod i=0 then kt:=false;
if kt=false then write('Khong phan so nguyen to')
else write('La so nguyen to');
readln
end.