# coding: utf-8

def _main():
    n, m = [int(i) for i in input().split()]
    a = [int(i) for i in input().split()]
    
    cards = [i for i in range(1, n+1)]
    
    for j in a:
        cards = [cards.pop(j-1)] + cards
    print(cards[0])

if __name__=='__main__':
    _main()