#include <iostream>
 
using namespace std;
 
int main()
{
   int T;
   int n;
   int* rungs;
   int str;
   cin >> T;
   for (int i = 1; i <= T; i++)
   {
      cout << "Case " << i << ": ";
      cin >> n;
      rungs = new int[n+1];
      rungs[0] = 0;
      for (int j = 0; j <= n-1; j++)
      {
         cin >> rungs[j+1];
      }
      str = -1;
      for (int jump = n; jump >= 0; jump--)
      {
         if (rungs[jump+1] - rungs[jump] == str)
            str += 1;
         else if (rungs[jump+1] - rungs[jump] > str)
            str = rungs[jump+1] - rungs[jump];
      }
      cout << str << endl;
      delete [] rungs;
   }
   return 0;
}
 

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