What does this C++ snippet output?

1#include <iostream>
2 
3struct A {
4  virtual void f() { std::cout << "A\n"; }
5};
6struct B : A {
7  void f() override { std::cout << "B\n"; }
8};
9void call(A a) { a.f(); }
10int main() {
11    B b;
12    call(b);
13}