why can I still give const value a new value [closed]

  anaconda, c++

enter image description hereThe book said I cannot change the value of const once I gave it a number´╝î but it seems I can still give it a number even if it was given.

using namespace std;
const int fansc(100);
cout<< fansc << endl; //output:100
int fansc(20);
cout<< fansc << endl;//output:20

Source: Windows Questions C++