Compilare: main.cpp: In function 'void build(ull)': main.cpp:27:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (ll i = 4; i <= N; i++) { ~~^~~~ main.cpp: In function 'int main()': main.cpp:41:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("hanoi4.in", "r", stdin); ^ main.cpp:42:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("hanoi4.out", "w", stdout); ^ main.cpp:44:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%lld", &n); ^