/* -*- coding: utf-8 -*-
 *
 * 817.cc:  No.817 Coin donation - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;
const int MAX_M = MAX_N * 2;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N], bs[MAX_N], xs[MAX_M], ds[MAX_M];

/* subroutines */

/* main */

int main() {
  int n, k;
  scanf("%d%d", &n, &k);
  k--;

  int m = 0;
  for (int i = 0; i < n; i++) {
    scanf("%d%d", as + i , bs + i);
    xs[m++] = as[i], xs[m++] = ++bs[i];
  }
  sort(xs, xs + m);
  m = unique(xs, xs + m) - xs;
  //printf("m=%d\n", m);

  for (int i = 0; i < n; i++) {
    int ai = lower_bound(xs, xs + m, as[i]) - xs;
    int bi = lower_bound(xs, xs + m, bs[i]) - xs;
    ds[ai]++, ds[bi]--;
  }
  for (int i = 1; i < m; i++) ds[i] += ds[i - 1];
  //for (int i = 0; i < m; i++) printf("%d ", ds[i]); putchar('\n');

  for (int i = 0; i + 1 < m; i++) {
    int &d = ds[i], l = xs[i + 1] - xs[i];
    ll dl = (ll)d * l;
    if (k >= dl) k -= dl;
    else {
      printf("%d\n", xs[i] + k / d);
      break;
    }
  }
  return 0;
}