program nguyen_to;
uses crt;
var n,i,d:integer;
begin
clrscr;
write('Nhap N: '); readln(n);
if n<2 then write(n,' khong phai so nguyen to')
else
begin
d:=0;
for i:=1 to n do
if n mod i=0 then d:=d+1;
if d=2 then write(n,' la so nguyen to')
else write(n,' khong phai so nguyen to');
end;
readln;
end.