#define _USE_MATH_DEFINES
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <cstring>
#include <queue>
#include <functional>
#include <set>
#include <map>
#include <string>
#include <cmath>
#include <math.h>
#include <complex>
#include <cassert>
#define rep(i,a,b) for (int i = (a); i < (b); i++)
#define case(i) cout<<"Case #"<<i<<": "
using namespace std;
typedef long long int ll;
typedef complex<double> com;
const int mod = 1e9 + 7;
const int MOD = 998244353;
const ll INF = 4e18;



int main() {
	int n, k; cin >> n >> k;
	vector<pair<int, int>> a(n);
	rep(i, 0, n) cin >> a[i].first >> a[i].second;
	int l = 0, r = 1e9;
	while (abs(l - r) > 1) {
		int mid = (l + r) / 2;
		ll cnt = 0;
		rep(i, 0, n) {
			if (a[i].first <= mid && a[i].second >= mid) {
				cnt += mid - a[i].first + 1;
			}
			if(a[i].second<mid){
				cnt += a[i].second - a[i].first + 1;
			}
		}
		if (cnt >= k) r = mid;
		else l = mid;
	}
	cout << l+1 << endl;
	return 0;
}