Drive the car

include <bits/stdc++.h>
using namespace std;

int main() {
	//code
	int n,a,b;cin>>n;
	while(n--){
	    cin>>a>>b;
	    int arr[a+1];
	    for(int i=0;i<a;i++){
	        cin>>arr[i];
	    }
	    arr[a] = b;
	    int *y = max_element(arr ,arr+a+1);
	    if(abs(*y-b)==0){cout<<-1<<endl;}
	    else{cout<<abs(*y-b)<<endl;}
	}
	return 0;
}