N, K = map(int,input().split())
query = []
for i in range (N) : 
    L, R = map(int,input().split())
    query.append([L,R])
ok = 10**9
ng = 0
while ok - ng > 1 : 
    mid = (ok + ng) // 2
    cnt = 0
    for L, R in query :
        if L > mid  : continue
        cnt += min(R, mid) - L + 1
    if cnt >= K : ok = mid
    else : ng = mid
print(ok)