#include <iostream>
#include <string>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <vector>
#include <cmath>
#include <cstdlib>
#include <queue>
#include <stack>
#include <iomanip>

using namespace std;

#define REP(i, n) for(ll i = 0;i < n;i++)
#define REPR(i, n) for(ll i = n;i >= 0;i--)
#define FOR(i, m, n) for(ll i = m;i < n;i++)
#define FORR(i, m, n) for(ll i = m;i >= n;i--)
#define REPO(i, n) for(ll i = 1;i <= n;i++)
#define ll long long
#define INF (ll)1 << 60
#define MINF (-1 * INF)
#define ALL(n) n.begin(),n.end()
#define MOD 1000000007
#define P pair<ll, ll>

ll n, k, now = 0, nn = 0;
vector<P> p;
int main() {
	cin >> n >> k;
	REP(i, n) {
		ll a, b;
		cin >> a >> b;
		p.push_back(P(a, 0));
		p.push_back(P(b + 1, 1));
	}
	sort(ALL(p));

	REP(i, p.size() - 1) {
		if (p[i].second == 0)nn++;
		else nn--;
		if (now + nn * (p[i + 1].first - p[i].first + 1) >= k) {
			cout << p[i].first + ((k - now) + nn - 1) / nn - 1;
			return 0;
		}
		else now += nn * (p[i + 1].first - p[i].first);
	}
}