https://www.luogu.com.cn/record/221494686

#include<bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
#define int long long

int ls[N << 5], rs[N << 5], cnt[N << 5], sum[N << 5];

int rt1, rt2, num;

void modify(int &k, int l, int r, int x, int v){
  if(!k) k = ++num; cnt[k] += v, sum[k] += x * v;
  if(l == r) return;
  int mid = l + r >> 1; 
  if(x <= mid) modify(ls[k], l, mid, x, v);
  else modify(rs[k], mid + 1, r, x, v);
}

int t = 0;

int query(int k, int l, int r, int x){
  if(cnt[k] <= x) return sum[k];
  int mid = l + r >> 1;
  if(cnt[ls[k]] >= x) return query(ls[k], l, mid, x);
  else return sum[ls[k]] + query(rs[k], mid + 1, r, x - cnt[ls[k]]);
}

void solve(){
  int n, m, f; cin >> n >> m >> f;
  vector<pair<int, int> >a(m + 1);
  for(int i = 1; i <= m; i++) cin >> a[i].first >> a[i].second;
  sort(a.begin(), a.end(), less<pair<int, int> >());
  for(int i = m; i > (n + 1) / 2; i--) { modify(rt2, 0, 2e5, a[i].second, 1); }
  for(int i = 1; i < (n + 1) / 2; i++) { modify(rt1, 0, 2e5, a[i].second, 1); }
  int maxn = -1;
  for(int i = (n + 1) / 2; i <= m - (n + 1) / 2 + 1; i++){
    int res = query(rt1, 0, 2e5, (n - 1) / 2) + a[i].second + query(rt2, 0, 2e5, (n - 1) / 2); 
    if(res <= f) maxn = max(maxn, a[i].first);
    modify(rt1, 0, 2e5, a[i].second, 1); modify(rt2, 0, 2e5, a[i + 1].second, -1);
  }
  if(maxn == -1) { cout << -1 << '\n'; return; }
  cout << maxn << '\n';
}

signed main(){
  int t = 1;
  //cin >> t;
  while(t--){
    solve();
  }
  return 0;
}