public static int NhapN(){
int n = int.Parse(Console.ReadLine());
public static int[] NhapMang(int n) {
for (int i = 0; i < n; i++) {
arr[i] = int.Parse(Console.ReadLine());
public static bool KiemTra2Muk(int a) {
public static int Bai166(int[] arr) {
for (int i = 0; i < arr.Length; i++) {
if (KiemTra2Muk(arr[i])) {
public static void Main()
double result = Bai166(arr);