Compilare: main.cpp: In function 'int main()': main.cpp:83:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("fallingb.in", "r", stdin); ^ main.cpp:84:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("fallingb.out", "w", stdout); ^ In function 'void build(int)': cc1plus: warning: iteration 6 invokes undefined behavior [-Waggressive-loop-optimizations] main.cpp:39:20: note: within this loop for (int k = 0; k < 8; ++k) { ~~^~~