#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
typedef long long ll;
#define int long long
#define rep(i,n) for (int i = 0; i < (int)(n); ++i)
#define all(x) (x).begin(),(x).end()
#define bit(n,k) ((n>>k)&1) /*nのk bit目*/
#define debug(x) cout << #x << ": " << x << endl;
using P = pair<int,int>;
#define INF 1001001001
#define LINF (1LL<<60)
template<class T> inline bool chmax(T& a, T b){ if(a<b){ a=b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b){ if(a>b){ a=b; return 1; } return 0; }

int32_t main() {
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) cin >> a[i];
  sort(all(a));
  int ans = a[0];
  rep(i, n-1) {
    if (a[i]+1 != a[i+1]) ans += a[i+1];
  }
  cout << ans << endl;
}