#include <bits/stdc++.h>
#define rep(i, l, r) for (int i = (l); i < (r); i++)
using namespace std;

typedef long long ll;

int main() {
    int N, ans = 0;
    cin >> N;
    vector<int> A(N);
    vector<bool> B(36, false);
    rep(i, 0, N) {
        cin >> A[i];
        B[A[i]] = true;
    }
    rep(i, 0, N) {
        if (!B[A[i] - 1]) ans += A[i];
    }
    cout << ans << "\n";
}