import strutils, sequtils

var n: int
n = parseInt(readLine(stdin))
var ans: int
var tmp: bool
var a = map(readLine(stdin).split(), parseInt)
for i in 0..<n:
  tmp = true
  for j in 0..<n:
    if a[i] - 1 == a[j]:
      tmp = false
  if tmp:
    ans += a[i]
echo ans