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

struct iofast_t {
    iofast_t() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} iofast;

struct uns_t {} uns;
template <typename Element, typename Head, typename ...Args>
auto vec(Element init, Head arg, Args ...args) {
    if constexpr (sizeof...(Args) == 0) return std::vector(arg, init);
    else return std::vector(arg, vec(init, args...));
}
template <typename Element, typename Head, typename ...Args>
auto vec(uns_t, Head arg, Args ...args) {
    return vec(Element(), arg, args...);
}

template <typename T, typename Compare = less<T>>
T &chmin(T &l, T r, Compare &&f = less<T>()) { return l = min(l, r, f); }
template <typename T, typename Compare = less<T>>
T &chmax(T &l, T r, Compare &&f = less<T>()) { return l = max(l, r, f); }

int main() {
    int n, k; cin >> n >> k;

    auto range = vec<tuple<int, int>>(uns, n);
    for (auto &[l, r] : range) {
        cin >> l >> r; ++r;
    }

    int left = 0, right = 1000000000;
    while (1 < right - left) {
        int mid = left + (right - left) / 2;

        int64_t sum = 0, equ = 0;
        for (auto [l, r] : range) {
            sum += max(0, min(mid, r) - l);
            equ += l <= mid && mid < r;
        }

        if (sum + equ < k) {
            left = mid;
        }
        else {
            right = mid;
        }
    }

    cout << right << endl;
}