Что выведет Go: pipeline из трёх стадий

package main

import "fmt"

func gen(n int) <-chan int {
    out := make(chan int)
    go func() {
        defer close(out)
        for i := 1; i <= n; i++ {
            out <- i
        }
    }()
    return out
}

func sq(in <-chan int) <-chan int {
    out := make(chan int)
    go func() {
        defer close(out)
        for v := range in {
            out <- v * v
        }
    }()
    return out
}

func main() {
    sum := 0
    for v := range sq(sq(gen(3))) {
        sum += v
    }
    fmt.Println(sum)
}