#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cmath>
using namespace std;
int n;
int nums[100010], numsc[100010];
int main() {
	int T;
	cin >> T;
	for(int nq = 0; nq != T; ++nq) {
		printf("Case #%d:\n", nq+1);
		cin >> n;
		for(int i = 0; i != n; ++i) {
		//	cin >> nums[i];
			scanf("%d", &nums[i]);
		}
		int beginK = -1, endK = 5000000, midK;
		bool can;
		while(endK - beginK > 1) {
			midK = (beginK + endK) / 2;
			for(int i = 0; i != n; ++i) {
				numsc[i] = nums[i];
			}
			numsc[0] -= midK;			
		 	can = true;//当前K可行
			for(int i = 1; i != n; ++i) {
				if(numsc[i] > numsc[i-1]) {
					if(numsc[i] - numsc[i-1] > midK) {
						numsc[i] -= midK;
					}
					else {
						numsc[i] = numsc[i-1] + 1;
					}
				}
				else if(midK < numsc[i-1] - numsc[i] + 1) {
					beginK = midK;
					can = false;//当前K不可行
					break;
				}else {
					numsc[i] = numsc[i-1] + 1;
				}
			}
			if(can) endK = midK;
		}
		cout << endK << endl;		
	}
	return 0;
}