#include <bits/stdc++.h>
using namespace std;
// #include <atcoder/all>
// using namespace atcoder;
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rep1(i, n) for (ll i = 1; i <= n; ++i)
#define reps(i, s, e) for (ll i = s; i <= e; ++i)
#define all(v) v.begin(), v.end()
using ll = long long;
using ld = long double;
using cp = complex<ld>;
using pa = pair<ll, ll>;
using tup = tuple<ll, ll, ll>;
using vp = vector<pair<ll, ll>>;
using vtup = vector<tuple<ll, ll, ll>>;
using st = string;
using vs = vector<string>;
using vc = vector<char>;
using vvi = vector<vector<ll>>;
using vvc = vector<vector<char>>;
using vi = vector<ll>;
const ll MOD1 = 1000000007;
const ll MOD2 = 998244353;
const ll INF = (1LL << 60);

int main() {
  ll n;
  cin >> n;
  vi a(n);
  rep(i, n) cin >> a[i];
  sort(all(a));

  ll ans = a[0];
  reps(i, 1, n - 1) if (a[i] - a[i - 1] != 1) ans += a[i];
  cout << ans << endl;
}