subarray_with_given_sum

def subArraySum(self,arr, n, s): 
       #Write your code here
        left = 0
        right = 0
        cur_sum = 0
        res = [0,0]
        while left<len(arr) or right < len(arr):
            if right == n and cur_sum < s:
                return -1
            elif left == n and cur_sum > s:
                return -1
            elif cur_sum < s:
                cur_sum += arr[right]
                right += 1
            elif cur_sum > s:
                cur_sum -= arr[left]
                left += 1
            else:
                res[0] = left+1
                res[1] = right
                return res