How do Sophie and Langdon finally find what they are looking for at the bank?

Once they are at the bank, Sophie and Langdon have to contend with a number of obstacles in a hurry. The security guard calls Interpol without Sophie and Langdon knowing, but they do know that, in general, the police are on their tail, so they must hurry. They are so close to accessing the contents of the safety deposit box when they discover that they must have an account number in addition to the key they have. With the authorities on the way to the bank, they only have moments to figure out the account number and retrieve the contents of the safety deposit box. Langdon remembers the ten-digit number written on the floor of the museum and Sophie rearranges it to form the Fibonacci sequence, a historically significant number sequence that her grandfather had taught her, which gives them access to the contents of the box.