Write a function named shift with arguments: x: a vector of any length. right: a length one logical vector with a default value of TRUE. The function should return a vector, the same type and length as the the input vector x. The elements should be appropriately shifted to the "right" if right is TRUE, or to the "left" if right is FALSE. If the input vector has length 0 or 1, simply return the input vector. The following shows example usage: letters [1:4] [1] "a" "b" "c" "d" shift (letters [1:4]) [1] "d" "a" "b" "c" shift (letters [1:4], right = FALSE) [1] "b" "c" "d" "a"