#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
using namespace std;

using ll = long long;
using P = pair<int, int>;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N, K;
    cin >> N >> K;
    vector<int> A(N), B(N);
    map<int, ll> mp;
    for(int i = 0; i < N; ++i){
        cin >> A[i] >> B[i];
        ++B[i];
        mp[A[i]] = -1;
        mp[B[i]] = -1;
    }

    int sz = 0;
    vector<int> compress;
    for(auto& [key, val] : mp){
        val = sz++;
        compress.emplace_back(key);
    }
    
    vector<ll> S(sz);
    for(int i = 0; i < N; ++i){
        S[mp[A[i]]] += 1;
        S[mp[B[i]]] -= 1;
    }
    for(int i = 0; i + 1 < sz; ++i) S[i + 1] += S[i];
    vector<ll> cnt(sz);
    for(int i = 0; i + 1 < sz; ++i){
        cnt[i] = S[i] * (compress[i + 1] - compress[i]);
    }
    
    ll sum = 0;
    int cursor = 0;
    while(cursor < sz && sum + cnt[cursor] < K){
        sum += cnt[cursor++];
    }

    K -= sum;
    int ans = compress[cursor] + (K - 1) / S[cursor];
    cout << ans << '\n';

    return 0;
}