#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define REP(i,m,n) for(int i=(int)(m); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define RREP(i,m,n) for(int i=(int)(m); i>=(int)(n); i--)
#define rrep(i,n) RREP(i,(n)-1,0)
#define all(v) v.begin(), v.end()
#define endk '\n'
const int inf = 1e9+7;
const ll longinf = 1LL<<60;
const ll mod = 1e9+7;
const ll mod2 = 998244353;
const ld eps = 1e-10;
template<typename T1, typename T2> inline void chmin(T1 &a, T2 b){if(a>b) a=b;}
template<typename T1, typename T2> inline void chmax(T1 &a, T2 b){if(a<b) a=b;}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n; cin >> n;
  vector<int> A(n); rep(i, n) cin >> A[i];
  set<int> st(all(A));
  ll sum = 0;
  rep(i, n) {
    if(!st.count(A[i]-1)) sum += A[i];
  }
  cout << sum << endk;
  return 0;
}