题解

#include<iostream>
#include<cstring>
using namespace std;
int main(){
int n;
cin >> n;
string a,b,c;
b = "123";
a = "4567";
c = b+a;
while(c.size()<n){
a = b;
b = c;
c = b + a;
}
cout << c[n-1];
return 0;
}