My program use iostream for reading data. Always when i use iostream i add this lines to turn off flushing after each line:

signed main(void) {
    cin.tie(nullptr)->sync_with_stdio(false);
    cout.tie(nullptr)->sync_with_stdio(false);
    // solution
    return 0;
}

But in this problem program with this lines getting WA#1, without - AC. Why?