#include <iostream>
#include <cassert>
#include <algorithm>
#include <vector>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int N; cin >> N;
  vector<int> A(N);
  for (int &i: A) cin >> 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;
}