Compilare: user.cpp: In function ‘void solve()’: user.cpp:87:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 1; j < V[i].size(); ++ j) ^ user.cpp:94:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 1; j < V[i].size(); ++ j) ^ user.cpp:107:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < V[x.x].size(); ++ i) ^ user.cpp: In constructor ‘InputReader::InputReader(const char*)’: user.cpp:21:43: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, SIZE, 1, input_file); ^ user.cpp: In member function ‘void InputReader::advance()’: user.cpp:48:47: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, SIZE, 1, input_file); ^ user.cpp: In function ‘void write()’: user.cpp:132:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("mine.out", "w", stdout); ^