Problem
Write a program that plays tic-tac-toe. The tic-tac-toe game is played on a 3x3 grid. The game is played by two players who take turns. The first player marks moves with a circle, the second with an X. The player who has formed a horizontal, vertical or diagonal sequence of 3 marks wins. Your program should print the game board, ask the user for the coordinates of the next mark, change players after every successful move and pronounce the winner.