#!/usr/bin/env python import itertools import sys from typing import List, Tuple def solve(circle: List[int]) -> int: def to_links(circle: List[int]) -> List[int]: links = [-1 for __ in range(len(circle) + 1)] cyclic = itertools.cycle(circle) next(cyclic) # Advance it by one for prev, cur in zip(circle, cyclic): links[prev] = cur return links def step(links: List[int], current: int) -> int: cup0 = links[current] cup1 = links[cup0] cup2 = links[cup1] links[current] = links[cup2] # Remove 3-tuple from the linked-list # Find destination dest = (current - 1) if current > 1 else (len(links) - 1) while dest in (cup0, cup1, cup2): dest = (dest - 1) if dest > 1 else (len(links) - 1) # Update our links links[cup2], links[dest] = links[dest], cup0 return links[current] # What's the next value in the cycle ? def to_answer(links: List[int]) -> int: next = links[1] res = 0 while next != 1: res = res * 10 + next next = links[next] return res current = circle[0] links = to_links(circle) for __ in range(100): current = step(links, current) return to_answer(links) def main() -> None: input = [line.strip() for line in sys.stdin.readlines()] assert len(input) == 1 print(solve([int(c) for c in input[0]])) if __name__ == "__main__": main()