#include <bits/stdc++.h> using namespace std; #define int long long void solve() { int n;cin>>n; int a[n+1]; int cavab=LLONG_MAX; for(int i=1;i<=n;i++)cin>>a[i]; for(int k=1;k<=n;k++){ vector<int>b(n+1); b[1]=a[1]; int c=0; for(int i=2;i<=k;i++){ b[i]=max(a[i],b[i-1]+1); if(i==k)c=max(a[i],b[i-1]+1); } int d=0; b[n]=a[n]; for(int i=n-1;i>=k;i--){ b[i]=max(a[i],b[i+1]+1); if(i==k)d=max(a[i],b[i+1]+1); } b[k] = max({b[k], (k>1?b[k-1]+1:b[k]), (k<n?b[k+1]+1:b[k])});; int co=0; for(int i=1;i<=n;i++)co=co+b[i]-a[i]; cavab=min(cavab,co); } cout<<cavab; } signed main() { ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0); int t=1;//cin>>t; while(t--)solve(); }