class Node:
    def __init__(self, data):
        self.data=data
        self.left=None
        self.right=None
        
def leftLeavesSum(root, isLeft, s):
    if not root:
        return
    if not root.left and not root.right and isLeft:
        s[0]+=root.data
    leftLeavesSum(root.left, 0, s)
    leftLeavesSum(root.right, 1, s)
    
def leftSum(root):
    sum=[0]
    leftLeavesSum(root, 0, sum)
    return sum[0]
    
root=Node(20)
root.left=Node(8)
root.right=Node(22)
root.left.left=Node(4)
root.left.right=Node(12)
root.left.right.left=Node(10)
root.left.right.right=Node(14)
    
print(leftSum(root))