This code reads two long long integers from standard input and prints their sum. It checks that exactly two values were successfully read before printing.

- The code does not handle the case where the sum of two long long values exceeds the maximum value that can be stored in a long long. Consider what happens when a and b are both very large positive numbers.
- The code does not handle the case where the sum is negative due to overflow. Think about how to detect or prevent overflow when adding two large numbers.