In file included from /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/utility:71:0,
from prog.cpp:1:
/usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_pair.h: In member function 'std::pair<_T1, _T2>& std::pair<_T1, _T2>::operator=(std::pair<_T1, _T2>&&) [with _T1 = const int, _T2 = bool, std::pair<_T1, _T2> = std::pair<const int, bool>]':
prog.cpp:9:59: instantiated from here
/usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_pair.h:127:2: error: assignment of read-only data-member 'std::pair<const int, bool>::first'