#include <iostream>
#include <vector>
#include <set>
#include <algorithm>
using namespace std;
int main()
{
	int N, i;
	cin >> N;
	if (N == 1) {
		cout << 0 << endl;
		return 0;
	}
	vector<int> P(N);
	int take = 0;
	int suzuki = 0;
	set<int> mySet;
	set<int>::iterator sit;
	for (i = 0; i < N; i++) {
		cin >> P[i];
		mySet.insert(i + 1);
	}
	for (i = N - 1; i >= 0; i--) {
		sit = mySet.find(P[i] + 1);
		if (sit != mySet.end()) {
			take += i + 1;
			mySet.erase(sit);
		}
		else {
			suzuki += i + 1;
			mySet.erase(mySet.begin());
		}
	}
	cout << take - suzuki << endl;
	return 0;
}