python

import sys

def solve() -> None:
    data = sys.stdin.read().strip()
    if not data:
        return
    n = int(data)

    # 初始两个字符串
    F0 = "123"          # 长度3
    F1 = "1234567"      # 长度7

    # 预计算长度序列，直到长度不小于 n
    lens = [3, 7]
    while lens[-1] < n:
        lens.append(lens[-1] + lens[-2])

    # 递归查找第 n 个字符
    def find(k: int, pos: int) -> str:
        if k == 0:
            return F0[pos - 1]   # pos 从1开始
        if k == 1:
            return F1[pos - 1]
        # k >= 2
        if pos <= lens[k-1]:
            return find(k-1, pos)
        else:
            return find(k-2, pos - lens[k-1])

    # 最大的k使得 lens[k] >= n
    k = len(lens) - 1
    result = find(k, n)
    print(result)

if __name__ == "__main__":
    solve()