def naive(n: int, xs: list[int]) -> list[int]:
    cards = list(range(n))
    for x in xs:
        v = cards[x]
        del cards[x]
        cards = [v] + cards

    return cards


def f(k: int, xs: list[int]) -> int:
    p = k
    for x in reversed(xs):
        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()))

cards = naive(N, A)
ans = cards[0] + 1
print(ans)