def solve():
    N,K=map(int,input().split())
    dn=[0]*(10**9+5)
    for i in range(N):
        a,b=map(int,input().split())
        dn[a]+=1
        dn[b+1]-=1
    c=0
    d=0
    for i,di in enumerate(dn):
        d+=di
        c+=d
        #print(i,c)
        if c>K:
            return i

print(solve())