type A = struct {
    data B b
    data C c
}
type D = struct {
    int x
    data C c
}
type F = struct {
    int x
}
type H = int
type B = struct {
    ref A ap
    int x
}
type C = struct {
    data F f
    data G g
    data H h
    data I i
}
type E = struct {
    data A a
    data C c
}
type G = struct {
    int x
}
type I = int