uses Crt;
Var N, i:integer;
Begin
clrscr;
write('Nhap vao mot so nguyen: ');
readln(N);
If N<=1 then
writeln('N khong la so nguyen to')
else
begin
i:=2;
while (N mod i<>0) do
i:=i+1;
if i=N then
writeln(N,' la so nguyen to!')
else
writeln(N,' khong phai la so nguyen to!');
end;
readln;