A standard US telephone keypad has letters on most of the numbers, to be used as a mnemonic aid in memorizing a phone number. Each letter is represented by a specific number, as follows: 2 = ABC 3 = DEF 4 = GHI 5 = JKL 6 = MNO 7 = PQRS 8 = TUV 9 = WXYZ Write a program to convert any phone number to its pure-numeric form. Input The input to your program will consist of multiple lines of phone numbers, consisting only of upper/lowercase letters and numbers. Output For each line of input, output the numeric form on a single line. Do not include any punctuation. Each line will contain no more than 63 characters. - View it on GitHub