#from collections import defaultdict
N, K = map(int, input().split())
K -= 1
shikiri = set()
LR = []
for i in range(N):
    a, b = map(int, input().split())
    shikiri.add(a)
    shikiri.add(b + 1)
    LR.append((a, b + 1))

nums = sorted(shikiri)
d = {}
id = 0
for num in nums:
    d[num] = id
    id += 1

L = len(d)
cnt = [0] * (L + 1)

for l, r in LR:
    l = d[l]
    r = d[r]
    cnt[l] += 1
    cnt[r] -= 1

# 左から累積
for i in range(L):
    cnt[i + 1] += cnt[i]
# nums と cnt で答えが出せる

total = 0
for i in range(L - 1):
    pos, nex = nums[i], nums[i + 1]
    # pos ~ nex - 1 までの nex - 1 - (pos - 1) = nex - pos 個の整数が cnt[i] 個*ずつ*存在する
    subtotal = (nex - pos) * cnt[i]
    
    if total + subtotal < K: # 次の区間に行く
        total += subtotal
    else: # この区間にK番目が存在する
        nokori = K - total
        sho, amari = divmod(nokori, cnt[i])
        ans = pos + sho
        exit(print(ans))