Write a program that reads a 4-bit binary number from the keyboard as a string and then converts it into decimal. for example, if the input is 1100, the output should be 12. (hint: break the string into substrings and then convert each substring to a value for a single bit. if the bits are b0, b1, b2, and b3, the decimal equivalent is 8b0+ 4b1+ 2b2+ b3.)