Reorganization

    1#include <bits/stdc++.h>
    2using namespace std;
    3using ll = long long;
    4const int inf = 1e9;
    5const long long INF = 1e17; //❄️
    6int main() {
    7    ios::sync_with_stdio(0); cin.tie(0); 
    8    int n, r; cin >> n >> r;
    9    map<int, int> p;
    10    p[r] = 0;
    11    for (int i = 1; i < n; i++) {
    12        cin >> r;
    13        auto it = p.lower_bound(r);
    14        if (it == p.begin()) {
    15            cout << "NO" << '\n';
    16            return 0;
    17        }
    18        --it;
    19        p[r] = 0;
    20        p[it->first]++;
    21        if (p[it->first] == 2) p.erase(it);
    22    }
    23    cout << "YES" << '\n';
    24    return 0;
    25}