Handling large I/O can slow down performance. Use fast I/O techniques like `scanf`/`printf` in C++ or `sys.stdin` in Python.

In competitive programming, when dealing with very large inputs and outputs, the time spent reading and writing data can become a bottleneck, especially if you're using standard input/output methods like cin and cout in C++. For such cases, using faster I/O methods like scanf and printf in C++ or reading in bulk using sys.stdin in Python can significantly improve performance. Instead of printing each line individually, accumulate output in a buffer and flush it all at once. This approach reduces the number of I/O operations and can save precious time in high-pressure scenarios. Additionally, if the problem permits, you can preprocess input into more manageable chunks, minimizing the number of reads. Fast I/O techniques can often be the difference between passing and failing large test cases.