import sys
input = sys.stdin.readline
sys.setrecursionlimit(10**7)

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

if N == 1:
    exit(print(0))

ans = 0
for i in range(1,N+1):
    p = P[i-1]
    if p == N:
        ans -= i
    else:
        ans += i

print(max(0,ans))