def f(k: int, inds: list[int]) -> int:
    p = k
    for x in reversed(inds):
        if p == 0:
            p = x
        elif x >= p:
            p -= 1

    return p


N, M = map(int, input().split())
A = list(map(lambda x: int(x)-1, input().split()))

ans = f(0, A) + 1
print(ans)