How to hide the pop up dialog box in fltk

[MAK001]

I am using this to create a pop-up that takes in users name:
void Controller::cli(){
int cmd = -1;
while (cmd != 0) {
string answer;
string menu = "What is your name";
const char *c = menu.c_str();
answer = fl_input(c,"Anonymous");

I just need the pop up to close after 'ok' is pressed.