program nguyento;
uses crt;
var n,i:integer;
funcition nt(n:integer):boolean;
var ok:boolean;
i:integer;
begin
ok:=true;
for i:=2 to n-1 do
if (n mod i)=0 then
ok:=ok and false;
if n<2 then
nt:=false
else
nt:=ok;
end;
begin
write('nhap n:');
readln(n);
if nt(n) then
write(n,'la so nguyen to')
else
write(n,' khong la so nguyen to');
readln;
end.