function dis(arr){
let cur = arr[1] - arr[0]
let max = cur
for(let i = 0; i < arr.length; i++) {
for(let k = i + 1; k < arr.length; k++) {
cur = Math.max(cur, arr[k] -arr[i])
max = Math.max(cur,max)
}
}
return max
}
console.log(dis(
[5,4,17]
))