foo.cpp: In function 'void hanoi(int, int, int, int)':
foo.cpp:6:9: error: 'cout' was not declared in this scope
         cout<<n<<' '<<from<<' '<<to_<<endl;
         ^
foo.cpp:6:39: error: 'endl' was not declared in this scope
         cout<<n<<' '<<from<<' '<<to_<<endl;
                                       ^