A sequence of n > 0 integers is called a jolly jumper if the absolute values of the difference between successive elements take on all the values 1 through n-1.
So the sequence [4,1,2,4] has absolute differences [3,1,2] which is equivalent to the set [1,2,3] (1 to n-1 where n is the length of original sequence) so it is therefore a jolly jumper.
Sequences have length n>0.
Assume n=1 is a jolly jumper.
Easy mode: Don't worry about stdin/stdout. Just a function that accepts arguments however and returns something that indicates jolly or not
Hard mode: Input on stdin (space separated), and output is "Jolly" / "Not jolly". Capitalization matters.
This is code golf.
EDIT: Sequences can contain negative integers and input on stdin is space separated.
$ jolly 2 -1 0 2 Jolly $ jolly 19 22 24 25 Jolly $ jolly 19 22 24 21 Not jolly