Thank you I got AC using fast i/o. Can you tell me why this (std::ios::sync_with_stdio(false);) speeds up input/output also when should we use fast i/o. ( I mean what is the maximum order of data read or written using cin/cout without fast cin/cout).

in MinGW build used by codeforces printf/scanf is much faster than cin/cout even if you'll add sync_with_stdio etc. Tried printing 10⁶ integers in custom test:

cout — 514 ms
cout with sync_with_stdio(false) — 467 ms
printf — 202 ms