"""
Algorithm Name: Max Sum of Sub Array
Time Complexity: O(n)
Explanation: arr = [3, 2, -4, 9]
at the start of the algorithm
assign current sum (max_sum_curr) = max sum(max_sum) = arr[0]
(for) iterate from arr[1] to arr[n] and do
  max_sum_curr = arr[i] if arr[i] > arr[i] + max_sum_curr
  else 
  max_sum_curr = max_sum_curr + arr[i]
  max_sum = max_sum if max_sum > max_sum_curr
  else 
  max_sum = max_sum_curr
end
return max_sum
"""

def max_sub_arr_sum(arr): 
    arr_size = len(arr)
    max_sum = arr[0]
    max_sum_curr = arr[0]
     
    for i in range(1, arr_size):
        max_sum_curr = max(arr[i], max_sum_curr + arr[i])
        max_sum = max(max_sum, max_sum_curr)
         
    return max_sum
    

# print("Enter array of numbers (Ex: 1 2 3 4 for [1, 2, 3, 4])")
arr = [3, 2, -4, 9] # list(map(int, input().split()))
print("Maximum Sub Array Sum is", max_sub_arr_sum(arr))