#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
#define rep(i, s, n) for (int i = s; i < n; i++)
#define rrep(i, s, n) for (int i = (n)-1; i >= (s); i--)
const long long MOD = 1e9 + 7, INF = 1e18;

signed main()
{
    int N, K;
    cin >> N >> K;
    map<int, int> mp;
    vector<int> a(N), b(N), v;
    for (int i = 0; i < N; i++)
    {
        cin >> a[i] >> b[i];
        a[i]--;
        v.push_back(a[i]);
        v.push_back(b[i]);
    }
    sort(v.begin(), v.end());
    int now = 0;
    map<int, int> inv;
    for (int i = 0; i < v.size(); i++)
    {
        if (mp.count(v[i]) == 0)
        {
            mp[v[i]] = now;
            inv[now] = v[i];
            now++;
        }
    }

    vector<int> imos(now + 1, 0);
    for (int i = 0; i < N; i++)
    {
        imos[mp[a[i]]] += 1;
        imos[mp[b[i]]] -= 1;
    }
    for (int i = 0; i < now; i++)
    {
        imos[i + 1] += imos[i];
    }

    rep(i, 0, now)
    {
        if (K - imos[i] * (inv[i + 1] - inv[i]) <= 0)
        {
            cout << inv[i] + (K + imos[i] - 1) / imos[i] << endl;
            return 0;
        }
        else
        {
            K -= imos[i] * (inv[i + 1] - inv[i]);
        }
    }
}