\begin{array}{c} \color{#db1616}{\texttt{#Khoadang09}} \end{array}

- Chặt nhị phân :

#include <bits/stdc++.h>
#define ll long long
using namespace std;
bool tknp(const vector<ll>& ar,ll X, ll l, ll r){
    if (l > r)  return false;     
    ll m = l + (r - l) / 2;
    if (ar[m] == X)  return true;
    if (ar[m] < X) return tknp(ar, X, m + 1, r);
    return tknp(ar,X, l, m - 1);
}

int main() {
    int n; ll X;
    cin >> n >> X;
    vector<ll> A(n);
    for (int i = 0; i < n; ++i) cin >> A[i];
    if (tknp(A, X, 0, n - 1)) cout << "Y" << endl;
    else  cout << "N" << endl;
}

#include <bits/stdc++.h>
using namespace std;
int n;
long long k;
vector<long long> a;
bool search(long long x) {
    long long l = 0, r = n - 1, mid;
    while (l <= r) {
        mid = l + (r - l) / 2;
        if (a[mid] == x) return true;
        if (a[mid] > x) r = mid - 1;
        else l = mid + 1;
    }
    return false;
}
int main() {
    cin >> n >> k;
    a.resize(n);
    for (int i = 0; i < n; i++) cin >> a[i];
    if (search(k)) cout << "Y";
    else cout << "N";
    return 0;
}