import collections

def solve():
    N,K=map(int,input().split())
    dn=collections.defaultdict(int)
    for i in range(N):
        a,b=map(int,input().split())
        dn[a]+=1
        dn[b+1]-=1
    c=0
    d=0
    i=0
    while True:
        i+=1
        d+=dn[i]
        c+=d
        #print(i,c)
        if c>K:
            return i

print(solve())