Compilare: user.cpp: In constructor ‘InputReader::InputReader(const char*)’: user.cpp:12:47: 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 member function ‘void InputReader::advance()’: user.cpp:34:51: 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 ‘int query(int, int)’: user.cpp:91:16: warning: ‘ansR.Node::val’ may be used uninitialized in this function [-Wmaybe-uninitialized] return ans.val; ^ user.cpp:61:33: warning: ‘ansR.Node::dr’ may be used uninitialized in this function [-Wmaybe-uninitialized] res.val = (a.val * pow[b.dr - b.st + 1] + ^ user.cpp:78:16: note: ‘ansR.Node::dr’ was declared here Node ansL, ansR; ^