import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long k = sc.nextLong();
        TreeMap<Integer, Integer> map = new TreeMap<>();
        int[] aArr = new int[n];
        int[] bArr = new int[n];
        for (int i = 0; i < n; i++) {
            aArr[i] = sc.nextInt();
            bArr[i] = sc.nextInt() + 1;
            map.put(aArr[i], 0);
            map.put(bArr[i], 0);
        }
        int idx = 0;
        for (int x : map.keySet()) {
            map.put(x, idx);
            idx++;
        }
        int[] imos = new int[idx];
        for (int i = 0; i < n; i++) {
            imos[map.get(aArr[i])]++;
            imos[map.get(bArr[i])]--;
        }
        for (int i = 1; i < idx; i++) {
            imos[i] += imos[i - 1];
        }
        for (int x : map.keySet()) {
            if (map.get(x) == idx - 1) {
                break;
            }
            int next = map.higherKey(x);
            int count = imos[map.get(x)];
            long size = next - x;
            if (k > size * count) {
                k -= size * count;
            } else {
                System.out.println(x + k / count);
                return;
            }
        }
    }
}