参考答案：

#include<iostream>
#include<algorithm>
#include<string>
using namespace std;
int main()
{
    string s;
    int n;
    cin >> n;

    for (int i = 1; i <= 1000; ++i) s += to_string(i);
    cout << s[n - 1] << endl;

    return 0;
}