import copy
import itertools
import time
import collections
import re
import functools



def p2():
    inp =[2,0,1,7,4,14,18] 
    nmbrs = {int(x): y + 1 for y, x in enumerate(inp[:-1])}
    last = int(inp[-1])

    for i in range(len(nmbrs) + 1, 30000000):
        if last not in nmbrs:
            nmbrs[last] = i
            last = 0
        else:
            prev, nmbrs[last] = nmbrs[last], i
            last = i - prev

    print(last)


start = time.time()
p2()
print(round(1000 * (time.time() - start), 2), "ms")