int a = scan.nextInt();

This line of code reads an integer input from the user and assigns it to the variable "a".

Assuming that this code is written in Java, it uses the Scanner class from the java.util package to read input from the user. The method nextInt() of the Scanner class is used to read an integer value from the input.

The input is expected to be entered through the console or standard input stream. The program will wait for the user to input an integer and press the enter key. Once the input is provided, the program will read the integer value and assign it to the variable "a".

Note that this code assumes that the input provided by the user is a valid integer. If the user enters a non-integer value, the program will throw an InputMismatchException. It is recommended to handle such exceptions to provide a better user experience and prevent the program from crashing.