#include <bits/stdc++.h> 
using namespace std;
using ll =long long;
#define all(v) v.begin(),v.end()
 #define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)

 int main() {
     ll N;cin>>N;
     vector<ll> A(N);
     map<ll,ll> S;
     for(ll i=0;i<N;i++) {
         cin>>A[i];
         S[A[i]]++;
     }
     ll ans=0;
     for(auto x:S) {
         if(S[x.first-1]==0) {
             ans+=x.first*x.second;
         }
     }
     cout<<ans<<endl;
 }