#!/usr/bin/env python3
from sys import stdin

def main():
    N = int(input())
    if N == 1:
        print(0)
        return
    P = list(map(int, input().split()))
    print((1 + N) * N // 2 - (P.index(N) + 1) * 2)
    return

if __name__ == '__main__':
    main()