program nt;
var
n,i:integer;
k:boolean;
begin
write(' nhap n : ');
readln(n);
k:=true;
if n<2 then k:= fasle
else
for i:= 2 to trunc(sqrt(n)) do
if n mod i = 0 then
begin
k:=false;
break;
end;
if k=true then write(n,' la so nguyen to ') else
write(n,' khong phai la so nguyen to');
readln;
end.