Input: [2, 1, 5, 2, 3, 2], S=7
Output: 2
// Explanation: The smallest subarray with a sum great than or equal to '7' is [5, 2].

Input: [2, 1, 5, 2, 8], S=7
Output: 1
// Explanation: The smallest subarray with a sum greater than or equal to '7' is [8].

Input: [3, 4, 1, 1, 6], S=8
Output: 3
// Explanation: Smallest subarrays with a sum greater than or equal to '8' are [3, 4, 1] or [1, 1, 6].

const smallest_subarray_with_given_sum = function(s, arr) {
  if (arr.length === 0) {
    return -1;
  }
  let size = 0;
  let min = Number.MAX_SAFE_INTEGER;
  let sum = 0;
  let left = 0
  for (let right = 0; right < arr.length; right++) {
    sum += arr[right];
    size++;
    if (sum >= s) {
      min = Math.min(min, size);
      sum -= arr[left++];
      size--;
    }
  }
  return min;
};