#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{
	int N,i;
	cin >> N;
	vector<int> A(N);
	for (i = 0; i < N; i++) {
		cin >> A[i];
	}
	sort(A.begin(), A.end());
	for (i = A.size() - 1; i > 0; i--) {
		if (A[i] == A[i - 1]+1) {
			A[i] = 0;
		}
	}
	int Sum = 0;
	for (i=0;i<A.size();i++){
		Sum += A[i];
	}
	cout << Sum << endl;
	return 0;
}