Keegan needs to choose a code for her safe. She is allowed to pick a code between 3 and 8 digits long (a “digit” is any of the numbers 0 through 9). Keegan wants to keep the code as short as possible while maintaining good security. What is the least number of digits Keegan can pick for her code so that a potential thief has no more than a 0.0001% chance of breaking into her safe on the first attempt?