Cryptarithmetic. Write a program to solve all puzzles of the form "Word1 plus Word2 equals Word3." The words should be input interactively. Use the Send More-Money program given in section 12.2.1 as a guide. As a refinement, make an interruptible version of the program, which can be stopped at any time if it is taking too long to find a solution. For the interruptible version, use the Search module instead of the Solve function.