#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
#define DUMP(x) cout << #x << " = " << (x) << endl;
#define FOR(i, m, n) for (ll i = m; i < n; i++)
#define IFOR(i, m, n) for (ll i = n - 1; i >= m; i--)
#define REP(i, n) FOR(i, 0, n)
#define IREP(i, n) IFOR(i, 0, n)
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) ll(x.size())

int main() {
  ll n;
  cin >> n;
  vector<ll> a(n);
  set<ll> st;
  FOR(i, 1, n + 1) { st.insert(i); }
  REP(i, n) { cin >> a[i]; }

  if (n == 1) {
    cout << 0 << endl;
    return 0;
  }

  ll ans = 0;
  IREP(i, n) {
    auto it = st.lower_bound(a[i] + 1);
    auto it2 = st.lower_bound(a[i]);
    if (it == st.end()) {
      if (it2 == st.end()) {
        ans -= i + 1;
        st.erase(st.begin());
      } else {
        st.erase(it2);
      }
    } else {
      ans += i + 1;
      st.erase(it);
    }
  }

  ll c = n * (n + 1) / 2;
  REP(i, n) {
    if (a[i] == n) {
      c -= 2 * (i + 1);
    }
  }
  ans = max(ans, c);
  ans = max(ans, 0LL);
  cout << ans << endl;
}