# ifndef ONLINE_JUDGE
# define _GLIBCXX_DEBUG
# endif
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using pii = pair<int, int>;
# define rep(i, n) for(int i = 0; i < (int)(n); ++i)
# define all(v) v.begin(), v.end()

int main(){
  constexpr char endl = '\n';
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed << setprecision(10);
  //input();
  int N;cin >> N;
  vi A(N);
  for(auto &&e : A)  cin >> e;
  //solve();
  int sum = 0;
  rep(i, N){
    bool ok = true;
    rep(j, N){
      if(A[i] == A[j]+1){
        ok = false;
        break;
      }
    }
    if(ok)  sum += A[i];
  }
  //output();
  cout << sum << endl;
}