#!/usr/bin/env python


def read():
    N, M = map(int, raw_input().split())
    return N, map(int, raw_input().split())


def work((N, shuffle)):
    deck = range(N)

    for idx in shuffle:
        idx -= 1

        tmp = deck[idx]
        del deck[idx]
        deck = [tmp] + deck

    print deck[0] + 1


if __name__ == "__main__":
    work(read())