// ki bood ke goft Ghatinga?

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef pair<pii,int> ppiii;

// vectors and Sets:
#define vc vector
#define pb push_back
#define all(c) (c).begin(), (c).end()

// pairs
#define mp make_pair
#define fr first
#define sc second

// execution time check and Debug
#define StartEX clock_t startExeTime = clock();
#define EndEX clock_t endExeTime = clock();
#define ExTime cerr << "\nTotal Execution Time is: " << double(-double(startExeTime)+double(endExeTime)) / CLOCKS_PER_SEC;
#define debug(x) cerr << #x << " : " << x << '\n'
#define endl "\n"

// time optimization
#define Heh ios::sync_with_stdio(false);cin.tie(0);
#define Bah ios::sync_with_stdio(false);
#pragma GCC optimize("Ofast")
// #pragma GCC target("avx,avx2,fma")

// useful functions
ll pw(ll a,ll b){
  ll ret = 1;
  ll mul = a;
  while(b > 0){
	if(b&1)
	  ret = (ret * mul);
	mul = (mul * mul);
	b >>= 1;
  }
  return ret;
}
ll pw(ll a,ll b,ll mod){
  ll ret = 1;
  ll mul = a;
  while(b > 0){
	if(b&1)
	  ret = (ret * mul) % mod;
	mul = (mul * mul) % mod;
	b >>= 1;
  }
  return ret;
}

ll to_int(string s){
  ll ret = 0;
  for(int i = 0 ; i < (int)s.size() ; i++) ret = 10 * ret + s[i] - '0';
  return ret;
}

bool deq(ld a , ld b){return (abs(a-b) < 0.000001);} // 10 ^ -6

const int MAXN = 1e6 + 16 , lg = 20;

int n;
int ha[MAXN];

vc<int> adj[MAXN];

pii spt[MAXN][lg];
int mxid(int l , int r){
  int j = 0;
  while((1 << (j+1)) <= r - l + 1) j++;
  return max(spt[l][j] , spt[r - (1 << j) + 1][j]).sc;
}

int build(int l , int r){
  if(l > r) return -1;
  if(l == r) return l;
  int id = mxid(l , r);
  int lf = build(l , id-1) , rt = build(id+1 , r);
  if(lf != -1) adj[id].pb(lf);
  if(rt != -1) adj[id].pb(rt);
  return id;
}

int ans = 0;
int dfs(int v , int h){
  ans = max(ans , h);
  int sm = 0;
  int mx = h;
  for(int u : adj[v]){
    int umx = dfs(u , h+1);
    sm += umx;
    mx = max(mx , umx);
  }
  ans = max(ans , sm - h);
  return mx;
}

int main()
{
  Heh;
  cin >> n;
  for(int i = 0 ; i < n ; i++) cin >> ha[i];
  for(int i = 0 ; i < n ; i++) spt[i][0] = {ha[i] , i};
  for(int j = 1 ; j < lg ; j++){
    for(int i = 0 ; i < n ; i++){
      spt[i][j] = spt[i][j-1];
      if(i + (1 << (j-1)) < n){
	spt[i][j] = max(spt[i][j] , spt[i + (1 << (j-1))][j-1]);
      }
    }
  }
  int root = build(0 , n-1);
  dfs(root , 0);
  cout << ans << endl;
}

// ki seda kard Patinga?