The problem Write a program that inputs two integers n and k, where n>=k. Your program should calculate the number of different ways that k bishops could be placed on an nXn chessboard. Structure your program using the backtracking scheme that we have used for the eight queens problem. What needs to be modified is the OK function. Input Your main program should loop asking the user for values of n and k. Output Each time through the loop, output n, k and the number of configurations. Program Termination The program will terminate if the user enters a value of -1 for n.