#include <bits/stdc++.h> using namespace std; #define int long long #define all(x) x.begin(), x.end() #define inf (int)3e18 #define ff first #define ss second using vi = vector<int>; using vii = vector<pair<int, int>>; using vvi = vector<vector<int>>; using pii = pair<int, int>; mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count()); const int MAX = 2e5 + 5; int a[MAX], b[MAX], pref[MAX], suff[MAX]; void solve() { int n; cin >> n; for (int i = 1; i <= n; i++) cin >> a[i]; for (int i = 1; i < n; i++) b[i] = a[i + 1] - a[i]; for (int i = 1; i < n; i++) { if (b[i] <= 0) { pref[i + 1] = 1 - b[i] + pref[i]; } else pref[i + 1] = pref[i]; } for (int i = n - 1; i > 0; i--) { if (b[i] >= 0) { suff[i] = suff[i + 1] + b[i] + 1; } else suff[i] = suff[i + 1]; } int ans = inf; for (int i = 1; i <= n; i++) { ans = min(max(pref[i], suff[i]), ans); } cout << ans; } signed main() { ios::sync_with_stdio(0); cin.tie(0); int tt = 1; // cin >> tt; while (tt--) solve(); }