import java.util.Scanner;

public class Main {
    static int a[] = new int[10000];
    static int s[] = new int[10000];

    static void init() {
        int i;
        a[1] = 1;
        s[1] = 1;
        for (i = 2; i < 10000; i++) {
            a[i] = a[i - 1] + (int) Math.log10((double) i) + 1;
            s[i] = s[i - 1] + a[i];
        }
    }

    static int Get(int n) {
        int i = 1;
        while (s[i] < n) i++;
        int pos = n - s[i - 1];
        return pos;
    }

    public static void main(String[] args) {
        init();
        Scanner scan = new Scanner(System.in);
        while(scan.hasNext()) {
            int c = scan.nextInt();
            System.out.println(Get(c));
        }
    }


}