Until an ATM can identify its user by odor or how hard he or she hugs it, you will have to log in with a personal identification number. Here are some ways to come up with a memorable four-digit code:

• Year of birth
  
• Year of first kiss
  
• Year of last kiss
  
• Number of friends you wish you had
  
• Number of horses you tell people you have
  
• Last four digits of pi
  
• Expiration date of milk that's been inside your refrigerator for a few years
  
• Number of states in the US if you were president
  
• Autoignition temperature of an acoustic guitar
  
• Four numbers that, when added together, equal a different number
  
• 1234
  
• Estimated number of days you'll spend alone in life, rounded to the nearest thousand