import times, strutils, sequtils, math, algorithm, tables, sets, lists, intsets
import critbits, future, strformat, deques
template `max=`(x,y) = x = max(x,y)
template `min=`(x,y) = x = min(x,y)
template `mod=`(x,y) = x = x mod y
template scan2 = (scan(), scan())
template scan3 = (scan(), scan())
let read* = iterator: string {.closure.} =
    while true: (for s in stdin.readLine.split: yield s)
proc scan(): int = read().parseInt
proc scanf(): float = read().parseFloat
proc toInt(c:char): int =
    return int(c) - int('0')




proc solve():int=
  var
    n = scan()
    m = newseqwith(n,scan()-1)
  for i in 0..<n-1:
    for j in i+1..<n:
      if (m[i]>=i and m[j]>=j) or (m[i]<i and m[j]<j):
        if m[i]>m[j]:
          result+=1
      elif m[j]<j and m[i]>=i:
        if m[i]>m[j]:
          result+=1
  
echo solve()