What does this Zig snippet output?

1const std = @import("std");
2const Flags = packed struct {
3    a: u1 = 1,
4    b: u1 = 0,
5    c: u1 = 1,
6    d: u1 = 1,
7};
8pub fn main() void {
9    const f = Flags{};
10    const byte: u4 = @bitCast(f);
11    std.debug.print("{d}\n", .{byte});
12}