import strutils, sequtils

var
  nm = stdin.readLine.split
  n = nm[0].parseInt
  m = nm[1].parseInt
  line = stdin.readLine.split
  stk = newSeqWith(n, 0)

for i in 0.. <n:
  stk[i] = i + 1

for i in 0.. <m:
  var ai = line[i].parseInt - 1
  var p = stk[ai]
  system.delete(stk, ai)
  stk.insert(p, 0)

echo stk[0]