import strutils, sequtils

proc f(s: string) :int = result = s.parseInt - 1

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

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

for i in 0.. <m:
  var p = stk[a[i]]
  system.delete(stk, a[i])
  stk.insert(p, 0)

echo stk[0]