Program received signal SIGSEGV, Segmentation fault.
0x00000001010b3153 in std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) () from /usr/local/opt/gcc/lib/gcc/4.9/libstdc++.6.dylib
(gdb) backtrace
#0  0x00000001010b3153 in std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) () from /usr/local/opt/gcc/lib/gcc/4.9/libstdc++.6.dylib
#1  0x000000010000cb13 in proceed_sentence(std::string const&, int&, int&, std::set<std::string, std::less<std::string>, std::allocator<std::string> >&, int, std::map<std::string, int, std::less<std::string>, std::allocator<std::pair<std::string const, int> > > const&, std::map<std::string, int, std::less<std::string>, std::allocator<std::pair<std::string const, int> > > const&, std::map<std::string, int, std::less<std::string>, std::allocator<std::pair<std::string const, int> > > const&) ()
#2  0x000000010000d153 in get_answer(std::string const&, int, int, int, std::map<std::string, int, std::less<std::string>, std::allocator<std::pair<std::string const, int> > > const&, std::map<std::string, int, std::less<std::string>, std::allocator<std::pair<std::string const, int> > > const&, std::map<std::string, int, std::less<std::string>, std::allocator<std::pair<std::string const, int> > > const&)
    ()
#3  0x000000010000d929 in main ()