#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

int main(){
  int N; cin >> N;
  vector<int> A(N);
  for(int i = 0; i < N; i++) cin >> A[i];
  sort(A.begin(), A.end());
  int ans = A[0];
  for(int i = 1; i < N; i++){
    if(A[i-1]+1 != A[i]) ans += A[i];
  }
  cout << ans << endl;
}