#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <algorithm>
#include <set>
#include <map>
#include <bitset>
#include <cmath>
#include <functional>
#include <iomanip>
#define vll vector<ll>
#define vvvl vector<vvl>
#define vvl vector<vector<ll>>
#define VV(a, b, c, d) vector<vector<d>>(a, vector<d>(b, c))
#define VVV(a, b, c, d) vector<vvl>(a, vvl(b, vll (c, d)));
#define re(c, b) for(ll c=0;c<b;c++)
#define rep(a,b,c) for(ll a=b;a<c;a++)
#define all(obj) (obj).begin(), (obj).end()
typedef long long int ll;
typedef long double ld;
using namespace std;

void get(vll &a){re(i,a.size()) scanf("%lld",&a[i]);}
void get(vvl &a){re(i,a.size()) re(j,a[0].size()) scanf("%lld",&a[i][j]);}
void print(vll &a){re(i,a.size()) cout<<a[i]<<(i==a.size()-1?"\n":" ");}
void print(vvl &a){re(i,a.size()) re(j,a[0].size())cout<<a[i][j]<<(j==a[0].size()-1?"\n":" ");}

int main() {
  map<ll, ll> mp;
  ll n, k;std::cin >> n >> k;
  re(i, n){
    ll a, b;std::cin >> a >> b;
    mp[a]++;
    mp[b+1]--;
  }

  ll pre = 0, num = 0, cnt = 0;
  for(auto e:mp){
    if(cnt + (e.first - pre)*num + e.second >= k){
      ll sa = k - cnt;
      ll tm = sa / num + (sa%num?1:0);
      std::cout << pre + tm << '\n';
      return 0;
    }
    ll x = e.first;
    cnt += (x - pre)*num + e.second;
    pre = x;
    num += e.second;
  }
}