# From the start node, find the node responsible
# for the target key
def findNode(start, key):
    current=start
    while distance(current.id, key) > \
          distance(current.next.id, key):
        current=current.next
    return current

# Find the responsible node and get the value for 
# the key
def lookup(start, key):
    node=findNode(start, key)
    return node.data[key]

# Find the responsible node and store the value 
# with the key
def store(start, key, value):
    node=findNode(start, key)
    node.data[key]=value