#include <bits/stdc++.h>
using namespace std;
const int INF = 2147483647;
const int MOD = 1048576;

int main(void) {
  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] != A[i] - 1) {
      ans += A[i];
    }
  }

  cout << ans << endl;
  return 0;
}