#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
int main() {
    // Input
    int N;
    cin >> N;
    vector<int> A(N);
    rep(i, N) cin >> A[i];

    // Calculation
    int score = 0;
    rep(i, N) {
        bool add = true;
        rep(j, N) if (A[j] == A[i] - 1) add = false;
        if (add) score += A[i];
    }

    // Output
    cout << score << endl;
}