Statement

Luca is supervising some students during a math test. To spare the tedious work, he gave each of them a calculator… but soon he realized that the students were using the calculators to sneakily exchange messages! A message is encoded as a number, where each digit corresponds to a letter (for example, the digit 0 corresponds to the letter `O', 1 to `I', 8 to `B' and so on; the precise mapping does not matter anyway). To prevent students from cheating, Luca replaced each calculator with a new model of safe calculators. These calculators are slightly different from standard calculators: (1) every digit has been removed except for digit 1, furthermore, it is not possible to press the digit 1 twice in a row; (2) to compensate for the lack of digits, Luca added a lot of operators: `\verb|+|' (addition), `\verb|-|' (subtraction), \linebreak `\verb|*|' (multiplication), `\verb|/|' (integer division), `\verb| (3) everything else has also been removed...