program snt;
uses crt;
var n,i:integer;
function nt(n:integer):boolean;
var i:integer;
begin
nt:=true;
if n<2 then nt:=false;
for i:=2 to n div 2 do
if n mod i=0 then nt:=false;
end;
begin
write('nhap n:');readln(n);
if nt(n) then writeln(n,' la so nguyen to')
else writeln(n,' ko la so nguyen to');
readln
end.