Compilare: user.cpp: In function ‘int main()’: user.cpp:61:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int bit = 0; bit < useful.size(); bit++) { ^ user.cpp:24:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("nop.in","r",stdin); ^ user.cpp:25:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("nop.out","w",stdout); ^ user.cpp:57:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (scanf("%d", &t); t > 0; t--) { ^ user.cpp:60:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &val); ^