What does this C++ snippet output?

1#include <iostream>
2#include <vector>
3int main() {
4    std::vector<int> v = {2, 4, 6};
5    for (auto& x : v) x += 1;
6    int sum = 0;
7    for (auto x : v) sum += x;
8    std::cout << sum << "\n";
9    return 0;
10}