uses crt;
var i,n,kt:integer;
begin
clrscr;
repeat
write('nhap n='); readln(n);
if n<=1 then writeln('ban da nhap sai, yeu cau ban nhap lai');
until n>1;
kt:=0;
for i:=2 to trunc(sqrt(n)) do
if n mod i=0 then kt:=1;
if kt=0 then writeln(n,' la so nguyen to')
else writeln(n,' khong la so nguyen to');
readln;
end.