func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long MOD = 1e9 + 7;   long long gcd(long long a, long long b) { return b == 0 ? a : gcd(b, a % b); }   long long lcm(long long a, long long b) { return a * (b / gcd(a, b)); }   const int MAXN = 600010;   set<int> g[MAXN];   int n, t, m, k;   int visited[MAXN];   void dfs(int i) {     visited[i] = 1;     for (auto x : g[i])       if (!visited[x]) dfs(x);     return;   }   int main() {     cin >> n;     pair<int, int> a[n];     for (long long i = 0; i < n; i++) cin >> a[i].first >> a[i].second;     sort(a, a + n);     int res = 0;     set<pair<int, pair<int, int> > > s;     for (long long i = 0; i < n; i++) {       auto x =           s.lower_bound({a[i].first, {-((long long)1e15), -((long long)1e15)}});       while (x != s.begin()) {         s.erase(s.begin());       }       auto it =           s.upper_bound({a[i].second, {-((long long)1e15), -((long long)1e15)}});       x = s.begin();       while (x != it) {         g[i].insert(x->second.second);         g[x->second.second].insert(i);         res++;         if (res >= n) {           cout <<  NO                 <<   n ;           return 0;         }         x++;       }       s.insert({a[i].second, {a[i].first, i}});     }     dfs(0);     for (long long i = 0; i < n; i++) {       if (!visited[i]) {         cout <<  NO ;         return 0;       }     }     if (res == n - 1)       cout <<  YES ;     else       cout <<  NO ;     return 0;   }   