import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N,M,*A = map(int,read().split())

card = list(range(1,N+1))
for x in A:
    x -= 1
    c = card[x]
    del card[x]
    card = [c] + card

print(card[0])