#include <iostream>
#include <vector>
using namespace std;
const int INF = 1000000000;
int main(){
	int N, K;
	cin >> N >> K;
	vector<int> A(N), B(N);
	for (int i = 0; i < N; i++){
		cin >> A[i] >> B[i];
	}
	int tv = INF;
	int fv = 0;
	while (tv - fv > 1){
		int mid = (tv + fv) / 2;
		long long ans = 0;
		for (int i = 0; i < N; i++){
			if (A[i] <= mid){
				ans += min(B[i], mid) - A[i] + 1;
			}
		}
		if (ans >= K){
			tv = mid;
		} else {
			fv = mid;
		}
	}
	cout << tv << endl;
}