#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
#define DUMP(x) cout << #x << " = " << (x) << endl;
#define FOR(i, m, n) for (ll i = m; i < n; i++)
#define IFOR(i, m, n) for (ll i = n - 1; i >= m; i--)
#define REP(i, n) FOR(i, 0, n)
#define IREP(i, n) IFOR(i, 0, n)
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) ll(x.size())

int main() {
  ll n;
  cin >> n;
  vector<ll> a(n);
  map<ll, bool> mp;
  REP(i, n) {
    cin >> a[i];
    mp[a[i]] = true;
  }
  ll ans = 0;
  REP(i, n) {
    if (!mp.count(a[i] - 1)) {
      ans += a[i];
    }
  }
  cout << ans << endl;
}