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

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    long long N, K;
    cin >> N >> K;
    vector<pair<long long ,int>> imos;
    for (int n = 0; n < N; ++n){
        long long a, b;
        cin >> a >> b;
        imos.emplace_back(make_pair(a, 1));
        imos.emplace_back(make_pair(b + 1, -1));
    } 
    sort(imos.begin(), imos.end());
    long long cum = 0;
    long long coin = 0;
    for (auto validx : imos){
        long long val = validx.first;
        int idx = validx.second;
        long long k = (val - coin) * cum;
        if (val == coin){
            cum += idx;
            continue;
        }else if (k < K){
            K -= k;
            coin = val;
            cum += idx;
            continue;
        }else if (k == K){
            coin = val - 1;
            break;
        }else{ // k > K
            coin += (K - 1LL) / cum;
            break;
        }
    }
    cout << coin << endl;
    return 0;
}