program ct
uses crt;
var k,i:integer;
begin
clrscr;
write('nhap k:=');readln(k);
if k<=1 then writeln('K khong phai so nguyen to') else
begin
i:=2;
while k mod i<>0 do i:=i+1;
if i=k then writeln(k,' la so nguyen to') else writeln(k,' khong la so nguyen to');
readln
end.