What does this C++ snippet output?

1#include <iostream>
2int main() {
3    int a = 1, b = 2;
4    int& r = a;
5    a = 8;
6    std::cout << r << "\n";  // r tracks a
7    r = b;                   // copy b's value into a
8    std::cout << a << "\n";
9    return 0;
10}