Buggy python submission (verdict: Runtime Error):
from sys import stdin

def main():

    input = stdin.readline

    N,K = map(int,input().split())

    A = list(map(int,input().split()))

    itta_list = set()
    idou_num = 0

    pos = 0

    for i in range(K):
        # itta_list記憶
        if pos not in itta_list:
            itta_list.add(pos)
        else:
            idou_num = i
            break

        # 次の街へ
        pos = A[pos] - 1
    else:
        ans_num = pos + 1
        print(ans_num)
        return

    roop_list = itta_list[itta_list.index(pos):]

    amari = (K - idou_num) % len(roop_list)

    ans_pos = roop_list[amari] + 1

    print(ans_pos)

if __name__ == "__main__":
    main()

Fixed submission:
from sys import stdin

def main():

    input = stdin.readline

    N,K = map(int,input().split())

    A = list(map(int,input().split()))

    itta_set = set()
    itta_list = []
    idou_num = 0

    pos = 0

    for i in range(K):
        # itta_list記憶
        if pos not in itta_set:
            itta_set.add(pos)
            itta_list.append(pos)
        else:
            idou_num = i
            break

        # 次の街へ
        pos = A[pos] - 1
    else:
        ans_num = pos + 1
        print(ans_num)
        return

    roop_list = itta_list[itta_list.index(pos):]

    amari = (K - idou_num) % len(roop_list)

    ans_pos = roop_list[amari] + 1

    print(ans_pos)

if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin

def main():

    input = stdin.readline

    N,K = map(int,input().split())

    A = list(map(int,input().split()))

    itta_list = []
    idou_num = 0

    pos = 0

    for i in range(K):
        # itta_list記憶
        if pos not in set(itta_list):
            itta_list.append(pos)
        else:
            idou_num = i
            break

        # 次の街へ
        pos = A[pos] - 1
    else:
        ans_num = pos + 1
        print(ans_num)
        return

    roop_list = itta_list[itta_list.index(pos):]

    amari = (K - idou_num) % len(roop_list)

    ans_pos = roop_list[amari] + 1

    print(ans_pos)

if __name__ == "__main__":
    main()

Fixed submission:
from sys import stdin

def main():

    input = stdin.readline

    N,K = map(int,input().split())

    A = list(map(int,input().split()))

    itta_set = set()
    itta_list = []
    idou_num = 0

    pos = 0

    for i in range(K):
        # itta_list記憶
        if pos not in itta_set:
            itta_set.add(pos)
            itta_list.append(pos)
        else:
            idou_num = i
            break

        # 次の街へ
        pos = A[pos] - 1
    else:
        ans_num = pos + 1
        print(ans_num)
        return

    roop_list = itta_list[itta_list.index(pos):]

    amari = (K - idou_num) % len(roop_list)

    ans_pos = roop_list[amari] + 1

    print(ans_pos)

if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin

def main():

    input = stdin.readline

    N,K = map(int,input().split())

    A = list(map(int,input().split()))

    itta_list = []
    idou_num = 0

    pos = 0

    for i in range(K):
        # itta_list記憶
        if pos not in itta_list:
            itta_list.append(pos)
        else:
            idou_num = i
            break

        # 次の街へ
        pos = A[pos] - 1
    else:
        ans_num = pos + 1
        print(ans_num)
        return

    roop_list = itta_list[itta_list.index(pos):]

    amari = (K - idou_num) % len(roop_list)

    ans_pos = roop_list[amari] + 1

    print(ans_pos)

if __name__ == "__main__":
    main()

Fixed submission:
from sys import stdin

def main():

    input = stdin.readline

    N,K = map(int,input().split())

    A = list(map(int,input().split()))

    itta_set = set()
    itta_list = []
    idou_num = 0

    pos = 0

    for i in range(K):
        # itta_list記憶
        if pos not in itta_set:
            itta_set.add(pos)
            itta_list.append(pos)
        else:
            idou_num = i
            break

        # 次の街へ
        pos = A[pos] - 1
    else:
        ans_num = pos + 1
        print(ans_num)
        return

    roop_list = itta_list[itta_list.index(pos):]

    amari = (K - idou_num) % len(roop_list)

    ans_pos = roop_list[amari] + 1

    print(ans_pos)

if __name__ == "__main__":
    main()

Buggy python submission (verdict: Runtime Error):
from sys import stdin

def main():

    input = stdin.readline

    N,K = map(int,input().split())

    A = list(map(int,input().split()))

    itta_list = []
    idou_num = 0

    pos = 0

    for i in range(K):
        # itta_list記憶
        if pos not in itta_list:
            itta_list.append(pos)
        else:
            idou_num = i
            break

        # 次の街へ
        pos = A[pos] - 1

    roop_list = itta_list[itta_list.index(pos):]

    amari = (K - idou_num) % len(roop_list)

    ans_pos = roop_list[amari] + 1

    print(ans_pos)

if __name__ == "__main__":
    main()

Fixed submission:
from sys import stdin

def main():

    input = stdin.readline

    N,K = map(int,input().split())

    A = list(map(int,input().split()))

    itta_set = set()
    itta_list = []
    idou_num = 0

    pos = 0

    for i in range(K):
        # itta_list記憶
        if pos not in itta_set:
            itta_set.add(pos)
            itta_list.append(pos)
        else:
            idou_num = i
            break

        # 次の街へ
        pos = A[pos] - 1
    else:
        ans_num = pos + 1
        print(ans_num)
        return

    roop_list = itta_list[itta_list.index(pos):]

    amari = (K - idou_num) % len(roop_list)

    ans_pos = roop_list[amari] + 1

    print(ans_pos)

if __name__ == "__main__":
    main()