View Compilation Error

0_0_17446930_7262.cpp: In function 'void dfs(int, int)':
0_0_17446930_7262.cpp:35:24: error: cannot bind 'std::ostream {aka std::basic_ostream<char>}' lvalue to 'std::basic_ostream<char>&&'
         cout<<ans[len-1]<<endl;
                        ^
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/iostream:39:0,
                 from 0_0_17446930_7262.cpp:1:
GCC4.9.2/x86_64-w64-mingw32/include/c++/ostream:602:5: note: initializing argument 1 of 'std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&&, const _Tp&) [with _CharT = char; _Traits = std::char_traits<char>; _Tp = number]'
     operator<<(basic_ostream<_CharT, _Traits>&& __os, const _Tp& __x)
     ^