#!/usr/bin/env python3
#fileencoding: utf-8

N, M = [int(i) for i in input().strip().split(" ")]
A = [int(i) for i in input().strip().split(" ")]

c = [i for i in range(1,N+1)]
for i in A:
    c.insert(0,c.pop(i-1))
print(c[0])