题解

#include<bits/stdc++.h>
using namespace std;

int main()
{
    string a="4567",b="123",c;
    long long n;
    cin >> n;
    while(true)
    {
        c=b+a;
        a=b;
        b=c;
        if (c.size()>n)
            break;
    }
    cout << c[n-1];
    return 0;
}