import sys
input = sys.stdin.readline

from heapq import heappush,heappop

N,X=map(int,input().split())
A=list(map(int,input().split()))

LIST=[0]*(N+3)

for a in A:
    if a<N+3:
        LIST[a]+=1

H=[]

for j in range(N+3):
    if LIST[j]==0:
        H.append(j)

H.sort()

for i in range(N+1):
    now=heappop(H)
    A.append(now)
    LIST[now]+=1
    if A[i]<N+3:
        LIST[A[i]]-=1

        if LIST[A[i]]==0:
            heappush(H,A[i])
            
if X-1<len(A):
    print(A[X-1])
else:
    k=X%(N+1)
    print(A[k+N])