#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
typedef long long ll;
using namespace std;

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 << endl;

    return 0;
}