Compute the sum of two given N-bit binary numbers.
The first line of the input file contains a positive integer T indicating the number of test cases. The first line of each test case is a positive integer N denoting the length of bits. The second and third lines are the two N-bit binary numbers. The first bit of each binary number is always 0, which guarantees that the sum of the two binary numbers can still be expressed as an N-bit binary number.
Level 1 : T<=100, N<=100
Level 2 : T<=200, N<=1000
Level 3 : T<=300, N<=5000
Level 4 : T<=400, N<=10000
For each test case, your program should print the sum in the same format as the binary numbers given in input.