The code should be written in C++

Task. BALLS Given are n boxes, which are initially empty. Ivancho has k balls. During the day, Ivancho puts k times a ball in a box and do not removes it. He may put a ball more than once in some of the boxes. Write program balls to compute the number of empty boxes at the end of the day. The program reads data by the standard input. On the first line, given are values of n and k. On each of the next k lines a box number (1,2,..n), in which Ivancho puts a ball, is given. On the standard output the program has to write an integer, which is the number of empty boxes at the end of the day. Constraints: 1