#include<iostream>
#include<algorithm>
#include<string>
#include<math.h>
#include<bitset>
#include <vector>
#include<bitset>
#include <iomanip>
#include <map>
#include <set>
#include <stack>
#include <deque>
#include <climits>
using namespace std;

int main() {
	
	int N;
	cin >> N;
	int A[40];
	for (int i = 1; i <= N; i++)cin >> A[i];
	map<int, int> MAP;
	for (int i = 1; i <= N; i++) {
		MAP[A[i]]++;
	}
	int answer = 0;
	for (int i = 1; i <= N; i++) {
		if (MAP[A[i] - 1] == 0)answer = answer + A[i];
	}
	cout << answer;

	
}