func findMaxAverage(nums []int, k int) float64 {
var sum float64 = 0.0
var ans float64 = - 114524
n := len(nums)
l, r := 0, 0
for r < n {
for r - l < k && r < n {
sum += float64(nums[r])
r ++
}
if r - l == k && l < n {
ans = max(ans, sum / float64(k))
sum -= float64(nums[l])
l ++
}
}
return ans
}