// I had brute forced for 1st subtask but getting run time error.
//Sample inputs are sucessfully executed.
#include <stdio.h>
#include<math.h>
#include<stdlib.h>
void decBinary(int arr[], int n);
int binaryDec(int arr[], int n);
int concat(int m, int n);
int binaryToDecimal(int n);
int main(void) {
// your code goes here
int t;
scanf("%d",&t);
while(t--){
int n,m,opd=0,j,p,r;
scanf("%d",&n);
int a[n],i,b[n*(n+1)/2];
for(i=0;i<n;i++){
scanf("%d",&a[i]);
}
// m=4;
// n=5;
for(i=0;i<n;i++){
for(j=i+1;j<n;j++){
p=concat(a[i],a[j]);
// p=binaryToDecimal(p);
// printf("%d ",p);
r=concat(a[j],a[i]);
// r=binaryToDecimal(r);
// printf("%d ",r);
b[opd]=abs(p-r);
// if(opd==11)
// printf("%d ",b[opd]);
opd++;
}
}
int large=0;
for(i=0;i<opd;i++){
if(b[i]>large)
large=b[i];
//c[i]=binaryToDecimal(b[i]);
}
printf("%d\n",large);
// i=concat(m,n);
//printf("%d",i);
}
return 0;
}
void decBinary(int arr[], int n)
{
int k = log2(n);
while (n > 0) {
arr[k--] = n % 2;
n /= 2;
}
}
// Funtion to convert the number
// represented as a binary array
// arr[] into its decimal equivalent
int binaryDec(int arr[], int n)
{
int ans = 0;
for (int i = 0; i < n; i++)
ans += arr[i] << (n - i - 1);
return ans;
}
// Function to concatenate the binary
// numbers and return the decimal result
int concat(int m, int n)
{
// Number of bits in both the numbers
int k = log2(m) + 1;
int l = log2(n) + 1;
// Convert the bits in both the integers
// to the arrays a[] and b[]
int a[40] = { 0 }, b[40] = { 0 };
// c[] will be the binary array
// for the result
int c[41] = { 0 };
decBinary(a, m);
decBinary(b, n);
// Update the c[] array
int in = 0;
for (int i = 0; i < k; i++)
c[in++] = a[i];
for (int i = 0; i < l; i++)
c[in++] = b[i];
// Return the decimal equivalent
// of the result
return (binaryDec(c, k + l));
}
int binaryToDecimal(int n)
{
int num = n;
int dec_value = 0;
// Initializing base value to 1, i.e 2^0
int base = 1;
int temp = num;
while (temp) {
int last_digit = temp % 10;
temp = temp / 10;
dec_value += last_digit * base;
base = base * 2;
}
return dec_value;
}
// Driver code