#include <bits/stdc++.h>
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
#endif
using ll = long long;
using ld = long double;
const ll INF = 1ll<<60;
const ld EPS = 1.0/1e9;
#define endl "\n"
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
#define del(x) sort(all(x)); x.erase(unique(all(x)),x.end());

int main(){
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  ll n; cin >> n;
  vector<ll>p(n);
  map<ll,ll>mp;
  rep(i,0,n){
    cin >> p[i]; mp[p[i]]=(i+1);
  }
  vector<ll>sum(n+1);
  rep(i,1,n+1){
    sum[i]+=sum[i-1];
    sum[i]+=mp[i];
  }
  ll ans=0;
  rep(i,0,n){
    ans=max(ans,sum[i]-mp[i+1]);
  }
  cout << ans << endl;
}