#include "iostream"
#include "climits"
#include "list"
#include "queue"
#include "stack"
#include "set"
#include "functional"
#include "algorithm"
#include "string"
#include "map"
#include "unordered_map"
#include "unordered_set"
#include "iomanip"
#include "cmath"
#include "random"
#include "bitset"
#include "cstdio"
#include "numeric"
#include "cassert"
#include "ctime"

using namespace std;

//constexpr long long int MOD = 1000000007;
//constexpr int MOD = 1000000007;
constexpr int MOD = 998244353;
//constexpr long long int MOD = 998244353;
constexpr double EPS = 1e-8;

//int N, M, K, T, H, W, L, R;
long long int N, M, K, T, H, W, L, R;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	cin >> N;
	vector<int>v(N);
	for (auto& i : v)cin >> i;
	if (v.back() == N) {
		if (N <= 2) {
			cout << 0 << endl;
			return 0;
		}
		else {
			cout << N * (N - 1) / 2 - N*2 << endl;
		}
	}
	else {
		for (int i = 0; i < N; i++) {
			if (v[i] == N) {
				cout << N * (N + 1) / 2 - (i + 1)*2 << endl;
				return 0;
			}
		}
	}
}