omizi.cpp: In function 'void read()': omizi.cpp:126: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result omizi.cpp:129: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result omizi.cpp:133: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result omizi.cpp:138: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result omizi.cpp: In function 'void DFS(int, int)': omizi.cpp:150: warning: comparison between signed and unsigned integer expressions In file included from /usr/include/c++/4.4/algorithm:62, from /usr/include/c++/4.4/i486-linux-gnu/bits/stdc++.h:63, from omizi.cpp:1: /usr/include/c++/4.4/bits/stl_algo.h: In function 'const _Tp& std::__median(const _Tp&, const _Tp&, const _Tp&) [with _Tp = caterpillar]': /usr/include/c++/4.4/bits/stl_algo.h:2268: instantiated from 'void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size) [with _RandomAccessIterator = caterpillar*, _Size = int]' /usr/include/c++/4.4/bits/stl_algo.h:5220: instantiated from 'void std::sort(_RAIter, _RAIter) [with _RAIter = caterpillar*]' omizi.cpp:181: instantiated from here /usr/include/c++/4.4/bits/stl_algo.h:89: error: passing 'const caterpillar' as 'this' argument of 'bool caterpillar::operator<(const caterpillar&)' discards qualifiers /usr/include/c++/4.4/bits/stl_algo.h:90: error: passing 'const caterpillar' as 'this' argument of 'bool caterpillar::operator<(const caterpillar&)' discards qualifiers /usr/include/c++/4.4/bits/stl_algo.h:92: error: passing 'const caterpillar' as 'this' argument of 'bool caterpillar::operator<(const caterpillar&)' discards qualifiers /usr/include/c++/4.4/bits/stl_algo.h:96: error: passing 'const caterpillar' as 'this' argument of 'bool caterpillar::operator<(const caterpillar&)' discards qualifiers /usr/include/c++/4.4/bits/stl_algo.h:98: error: passing 'const caterpillar' as 'this' argument of 'bool caterpillar::operator<(const caterpillar&)' discards qualifiers