[R] how to use list index to get vector

[Luke]

I have a simple question, but I couldn't find the answer in R manuals.

Assume I have a list:
> foo <- list()
> foo[[1]] <- c(1, 2, 3)
> foo[[2]] <- c(11,22,33)
> foo[[3]] <- c(111,222,333)
> foo
[[1]]
[1] 1 2 3

[[2]]
[1] 11 22 33

[[3]]
[1] 111 222 333

How to use list index to get a vector of, say, the first elements of
list elements?
That is, how to get a vector c(1, 11, 111) from foo?

foo[[]][1] doesn't work.

-Luke