#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)

using std::cin;
using std::cout;
using std::vector;

int main() {
	int n;
	cin >> n;
	
	vector<int> a(n);
	rep(i, n) cin >> a[i];
	
	sort(a.begin(), a.end());
	
	int ans = a[0];
	for (int i = 1; i < n; ++i) {
		if (a[i] > a[i - 1] + 1) ans += a[i];
	}
	cout << ans << '\n';
	
	return 0;
}