Compilare: main.cpp: In function 'void gen()': main.cpp:38:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (ans.size() == k) { ~~~~~~~~~~~^~~~ main.cpp: In function 'int main()': main.cpp:57:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("combinari.in","r",stdin); ^ main.cpp:58:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("combinari.out","w",stdout); ^