ios::sync_with_stdio(0);

ios::sync_with_stdio(0) is a line of code that is used in C++ to synchronize the input and output streams with the standard C input and output streams. This helps to reduce the time taken to read or write data from the input/output streams.

By default, the C++ input and output streams are not synchronized with the C input and output streams, which can cause delays and performance issues. However, by using ios::sync_with_stdio(0), the C++ input and output streams are synchronized with the C input and output streams, which can improve performance significantly.

It is important to note that this line of code should be used only when using standard input and output streams (cin and cout) in C++ programs. If you are using other input/output libraries or functions, such as scanf or printf, this line of code is not necessary.