Compilare: user.cpp: In function ‘void bck(int)’: user.cpp:35:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(size_t i = 0; i < len; ++i) ^ user.cpp: In function ‘int main()’: user.cpp:54:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("numere7.in", "r", stdin); ^ user.cpp:55:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("numere7.out", "w", stdout); ^