from collections import defaultdict

from heapq import heappop, heappush

def getlist():
	return list(map(int, input().split()))

N, K = getlist()
D = defaultdict(int)
for i in range(N):
	A, B = getlist()
	D[A] += 1
	D[B + 1] -= 1

L = []
for i in D:
	L.append([i, D[i]])

L = sorted(L)

Kval = K
n = 0
for i in range(len(L) - 1):
	n += L[i][1]
	a = L[i][0]
	b = L[i + 1][0]
	if (b - a) * n >= Kval:
		print(a + int((Kval - 1) // n))
		break
	else:
		Kval -= (b - a) * n