#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0; i<(n); i++)
#define INF ((1LL<<62)-(1LL<<31))
#define all(a)  (a).begin(),(a).end()
#define rall(a)  (a).rbegin(),(a).rend()
typedef long long ll;
typedef pair<ll,ll> pl;

//const ll mod=1000000007;

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