Compilare: user.cpp: In function ‘void cb(int)’: user.cpp:66:48: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < el.size(); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:100:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < it->size(); ++i) ^ user.cpp:77:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.in", "r", stdin); ^ user.cpp:78:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.out", "w", stdout); ^