Assume that we have a pattern like the following: ([n][letter])+ in which n is an integer number and letter is one of the lowercase letters from a-z. For example, 2a and 3b are valid expressions based on our pattern. Also, + at the end of the pattern means that we have at least one expression (string) or more than one expression attached. For instance, 2a4b is another valid expression which is matched with the pattern. In this question, we want to convert these valid expressions to a string in which letters are repeated n times. o Read an expression (string) from user and print the converted version of the expression in the output. o Check if input expression is valid. For example, 2ab is not a valid expression. If the expression is not valid, print Invalid Input in the output and ask user to enter another expression. o Sample input1 = 2a, output = aa o Sample input2 = 2a3b, output = aabbb.

**I need a c program(not c++)**