/*
Description:
If you have completed the Tribonacci sequence kata, you would know by now that mister Fibonacci has at least a bigger brother. If not, give it a quick look to get how things work.

Well, time to expand the family a little more: think of a Quadribonacci starting with a signature of 4 elements and each following element is the sum of the 4 previous, a Pentabonacci (well Cinquebonacci would probably sound a bit more italian, but it would also sound really awful) with a signature of 5 elements and each following element is the sum of the 5 previous, and so on.

Well, guess what? You have to build a Xbonacci function that takes a signature of X elements - and remember each next element is the sum of the last X elements - and returns the first n elements of the so seeded sequence.

xbonacci {1,1,1,1} 10 = {1,1,1,1,4,7,13,25,49,94}
xbonacci {0,0,0,0,1} 10 = {0,0,0,0,1,1,2,4,8,16}
xbonacci {1,0,0,0,0,0,1} 10 = {1,0,0,0,0,0,1,2,3,6}
xbonacci {1,1} produces the Fibonacci sequence
*/

function Xbonacci(s,n){
  if (s.length>n) return s.slice(0,n);
  let sum=[...s]
  for (let i=0;sum.length<n;i++)
  {sum.push(sum.slice(i,sum.length).reduce((a,b)=>a+b,0))}
  return sum
}
