fast i/o in c++

The "sync_with_stdio(false)" statement is used to turn off synchronization between the C and C++ standard streams. This can improve the speed of input/output operations. The "cin.tie(NULL)" statement unties the cin stream from the cout stream, which also can improve the speed of input/output operations. Finally, the "ios_base::sync_with_stdio(false)" statement is used to untie the synchronization between C and C++ standard streams, which can further enhance the speed of input/output operations.