#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;

#define ll long long
#define rep(i, n) for (int i = 0; i < (n); i++)
#define P pair<int, int>
#define LP pair<ll, ll>
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define all(s) s.begin(), s.end()
#define rall(s) s.rbegin(), s.rend()
template<class T>
void chmax(T& a, T b) { a = max(a, b); };
template<class T>
void chmin(T& a, T b) { a = min(a, b); };

int main() {
  int n;
  cin >> n;
  vector<bool> card(40);
  rep(i,n) {
    int a;
    cin >> a;
    card[a] = true;
  }
  int ans = 0;
  for (int i = 1; i <= 35; i++) {
    if (card[i] && !card[i-1]) ans += i;
  }
  cout << ans << endl;
  return 0;
}