Compilare: user.cpp: In function ‘int main()’: user.cpp:103:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (sols.size()>k) { ^ user.cpp:122:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<sols.size();i++) { ^ user.cpp:74:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("union.in","r",stdin); ^ user.cpp:75:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("union.out","w",stdout); ^