Write a program to check if an input is a valid hashtag(starts with #, contains only letters, numbers, and underscore, no space or special characters).1)Name your program hashtag. c.2)The user input ends with the user pressing the enter key (a new line character).3)Library function isalpha(), isdigit(), and isalnum()arenot allowed inthis program.4)Use getchar() to read in the input.