Compilare: user.cpp: In function ‘void del(int, int, int)’: user.cpp:21:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<v[b].size(); ++i) ^ user.cpp: In function ‘void euler(int)’: user.cpp:66:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<sol.size(); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:73:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("domino.in", "r", stdin); ^ user.cpp:74:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("domino.out", "w", stdout); ^ user.cpp:76:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i", &n); ^ user.cpp:79:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i %i", &a, &b); ^