What does this C++ snippet output?

1#include <iostream>
2int main() {
3    auto fib = [](int n) {
4      int a = 0, b = 1;
5      for (int i = 0; i < n; i++) {
6        int t = a + b;
7        a = b;
8        b = t;
9      }
10      return a;
11    };
12    std::cout << fib(10) << "\n";
13}