#include <bits/stdc++.h>
using ll = long long;
using std::cin;
using std::cout;
using std::endl;
std::mt19937 rnd(std::chrono::steady_clock::now().time_since_epoch().count());
template <class T>
inline bool chmax(T &a, T b)
{
  if (a < b)
  {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
inline bool chmin(T &a, T b)
{
  if (a > b)
  {
    a = b;
    return 1;
  }
  return 0;
}

const int inf = (int)1e9 + 7;
const long long INF = 1LL << 60;

void solve([[maybe_unused]] int CASE)
{
  int n;
  cin >> n;
  std::vector<int> a(n);
  for (int i = 0; i < n; ++i)
  {
    cin >> a[i];
  }
  std::sort(a.begin(), a.end());
  int res = 0;
  for (int i = 0; i < n; ++i)
  {
    if (not std::binary_search(a.begin(), a.end(), a[i] - 1))
      res += a[i];
  }
  cout << res << "\n";
}

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

  int kkt = 1;
  // cin >> kkt;
  for (int jupi = 1; jupi <= kkt; jupi++)
    solve(jupi);
  return 0;
}