#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
using ll = long long;
#define rep(i, n) for (int i = 0; i < (n); ++i)

int main() {
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) cin >> a[i];
  set<int> s(a.begin(), a.end());
  int ans = 0;
  rep(i, n) {
    if (s.count(a[i] - 1) == 0) ans += a[i];
  }
  cout << ans << endl;
  return 0;
}