#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
#define SS ios_base::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
#pragma optimize("g", on)
#pragma GCC optimize("03")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,avx2,mmx,fma,avx,tune=native")
#define int long long
#define all(x) x.begin(),x.end()
#define F first
#define S second
using namespace std;
// using namespace __gnu_pbds;
// #define ordered_set tree<int,null_type,less_equal<int>,rb_tree_tag,tree_order_statistics_node_update>
const int LG = 21,N = 2e5+1,inf = 1e18,MOD = 998244353;
const double eps = 1e-9;
int T;
void solve() {
int n;
cin>>n;
int a[n+2]={};
for(int i=1;i<=n;i++){
cin>>a[i];
}
int pref[n+1]={},prmx[n+2]={};
int suf[n+2]={},sufmx[n+2]={};
for(int i=2;i<=n;i++){
pref[i]=pref[i-1]+max(0ll,a[i-1]-a[i]+1);
}
for(int i=n-1;i>=1;i--){
suf[i]=suf[i+1]+max(0ll,a[i+1]-a[i]+1);
}
int ans=inf;
for(int i=1;i<=n;i++){
ans=min(ans,max(pref[i],suf[i]));
}
cout<<ans;
return;
}
signed main() {
// freopen("deleg.in","r",stdin);
// freopen("deleg.out","w",stdout);
SS
int t = 1;
if (T) {
cin >> t;
}
while (t--) {
solve();
}
}
/*
*/
