Compilare: user.cpp: In function ‘void f(int, int)’: user.cpp:14:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < H[x % M].size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:28:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("hashuri.in", "r", stdin); ^ user.cpp:29:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("hashuri.out", "w", stdout); ^ user.cpp:30:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:33:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &op, &x); ^