#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin >> N;
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  int ans = 0;
  for (int i = 0; i < N; i++){
    bool ok = true;
    for (int j = 0; j < N; j++){
      if (A[j] == A[i] - 1){
        ok = false;
      }
    }
    if (ok){
      ans += A[i];
    }
  }
  cout << ans << endl;
}