#!/usr/bin/env python3
# from typing import *

import sys
import io
import math
import collections
import decimal
import itertools
import bisect
import heapq


def input():
    return sys.stdin.readline()[:-1]


# sys.setrecursionlimit(1000000)

# _INPUT = """# paste here...
# """
# sys.stdin = io.StringIO(_INPUT)

INF = 10**10

def solve(N, P):
    if N == 1:
        return 0

    s = N*(N+1)//2
    ans = 0
    for i in range(N):
        if P[i] == N:
            return s - (i+1)*2

N = int(input())
P = list(map(int, input().split()))
print(solve(N, P))