dalao救救 90分 第二个测试点没过 附第二个测试点的数据

#include<iostream>
#include<string>
#include<cmath>
using namespace std;

int main()
{
    string s;
    cin >> s;
    long long n;
    cin >> n;
    long long i = n;
    for (int factor = log2(n / s.length()) + 1; factor > 0; factor--)
    {
        if (i == s.length() * pow(2, factor - 1) + 1)
        {
            i = s.length() * pow(2, factor - 1);
        }
        else if (i > s.length() * pow(2, factor - 1) + 1)
        {
            i = i - s.length() * pow(2, factor - 1) - 1;
        }
    }
    cout << s[i - 1];
    return 0;
}

测试点2 输入：ABCDEFGHIJKLMNOPQRSTUVWXYZ 99999999999999999 输出：D