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

list = []

for n in range(1, N + 1):
    list.append(n)
    
for i in range(M):
    num = A[i]
    list.insert(0, list[num - 1])
    del list[(A[i])]
print(list[0])