#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main() {
    int n;
    cin >> n;

    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    sort(a.begin(), a.end());

    int s = 0;
    for (int i = 0; i < n; i++) {
        if (i == 0 || a[i - 1] + 1 != a[i]) s += a[i];
    }
    cout << s << endl;

    return 0;
}