#include <iostream>
using namespace std;
int main()
{
	int t;
	cin>>t;
	while(t--)
	{
	    int n,k;
	    cin>>n>>k;
	    int A[n];
	    int i;
	    int m=0;
	    for(i=0;i<n;i++)
	    {
	        cin>>A[i];
	        if(A[i]>k&&A[i]>m)
	        m=A[i];
	    }
	    if(m==0)
	    cout<<"-1"<<endl;
	    else
	    cout<<m-k<<endl;
	}
	return 0;
}

Problem Description

Suppose you are car driver and you have to drive a car on a track divided into “N” no. of sub-tracks. You are also given the value of “K” i.e. the total kilometers a car can drive on each sub-track.

If the car can’t cover a sub-track, you can add any unit of Petrol in it. With each unit of petrol added, the total kilometers your car can travel will increase by one unit .

Input:
The first line of input contains an integer T denoting the no of test cases. Then T test cases follow. Each test case contains two space separated integers N and K. The second line of each test case contains N space separated integers (A[]) denoting the distance of each N sub-tracks.

Output:

For each test case in a new line you have to print out the minimum unit of Petrol your car require to cover all the sub-tracks. If no extra unit of petrol is required, print -1.

Constraints:
1<=T<=100
1<=N,K<=200
1<=A[]<=1000

• Test Case 1

  Input (stdin)

  2
  5 7
  2 5 4 5 2
  5 4
  1 6 3 5 2
  

  Expected Output

  -1
  2

• Test Case 2

  Input (stdin)

  1
  5 7
  2 5 4 5 2
  

  Expected Output

  -1