#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int N, K;
vector<pair<int,int>> query;

signed main() {

  cin >> N >> K;

  query.resize(N);
  for (int i = 0; i < N; ++i) {
    cin >> query[i].first >> query[i].second;
  }

  int ok = (int)1e9, ng = 0;
  while (abs(ok - ng) > 1) {
    int mid = (ok + ng) / 2;
    ll cnt = 0;
    for (auto& q : query) {
      int a, b;
      tie(a, b) = q;
      if (b <= mid) cnt += b - a + 1;
      else if (a <= mid) cnt += mid - a + 1;
    }
    if (cnt >= K) ok = mid;
    else ng = mid;
    // cerr << ok << ' ' << ng << endl;
  }

  cout << ok << endl;

}