#threading s barrijerom

import threading

result = 0
lock = threading.Lock()
barrier = threading.Barrier(3)

def add (start, stop):
    global result
    global barrier
    for i in range(start, stop)
        with lock:
            result = result + i**2

    barrier.wait()

t1 = threading.Thread(target = add, args(0, 15001))
t2 = threading.Thread(target = add, agrs(15001, 30001))
t3 = threading.Thread(target = add, agrs(30001, 500001))

t1.start()
t2.start()
t3.start()

t1.join()
t2.join()
t3.join()

print(result)