#include <bits/stdc++.h>
using namespace std;
int main() {
    int n; long long k; cin >> n >> k;
    map<long long, long long> m;
    for (int i = 0; i < n; i++) {
        long long a, b; cin >> a >> b;
        m[a]++; m[b+1]--;
    }
    long long cur = 0; long long prev = 0;
    for (auto it: m) {
        if (k - (it.first - prev) * cur <= 0) {
            cout << prev + (k + cur-1) / cur - 1 << endl;
            return 0;
        }
        k -= (it.first - prev) * cur;
        prev = it.first;
        cur += it.second;
    }
    return 0;
}