/*
* this code is made by crazyacking
* Verdict: Accepted
* Submission Date: 2015-05-30-22.26
* Time: 0MS
* Memory: 137KB
*/
#include <queue>
#include <cstdio>
#include <set>
#include <string>
#include <stack>
#include <cmath>
#include <climits>
#include <map>
#include <cstdlib>
#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
#define  LL long long
#define  ULL unsigned long long
using namespace std;
const int MAXN=100010;

int num[MAXN],n,T,tmp[MAXN];
inline bool check(int l){
    for(int i=1;i<=n;i++)
    tmp[i]=num[i];
    tmp[1]=num[1]-l;
    for(int i=2;i<=n;i++)
        if(num[i]+l<=tmp[i-1])
            return false;
        else 
            tmp[i]=max(num[i]-l,tmp[i-1]+1);
    return true;
}
int main()
{
    scanf("%d",&T);
    for (int Rt=1;Rt<=T;Rt++)
        {
        scanf("%d",&n);
        cout<<"Case #"<<Rt<<‘:‘<<endl;
        for(int i=1;i<=n;i++) scanf("%d",&num[i]);
        int l=0,r=1000000,ans=0;
        while(l<=r){
            int mid=(l+r)>>1;
            if(check(mid)){
                ans=mid;
                r=mid-1;
            }else{
                l=mid+1;
            }
        }
        cout<<ans<<endl;
    }
    return 0;
}