Modular arithmetic helps prevent overflow and is often required in problems involving large numbers.

Modular arithmetic is crucial in competitive programming, especially when working with large numbers that can easily exceed the maximum value a data type can store. Using modular arithmetic, you can keep numbers within a manageable range by taking the remainder of a division operation. This is especially common in combinatorics, where results can quickly grow too large. Many competitive programming problems explicitly require answers modulo a large prime number (like 10^9+7) to prevent overflow and ensure consistent results. Understanding how to apply modular arithmetic helps you avoid overflow errors and solve problems that deal with large numbers efficiently.