>>> f(3)
0010111

>>> f(3)
0123456789876543210

>>> f(3)
001010011110111

import java.util.Scanner;
import java.util.ArrayList;

public class Checker {
    public static void main(String[] args) throws Exception {
        int substringLength = Integer.parseInt(args[0]);

        Scanner sc = new Scanner(System.in);
        sc.useDelimiter("");

        ArrayList<Character[]> active = new ArrayList<Character[]>();

        Character[] current = new Character[substringLength],
            compare, prev;

        for (int i = 0; i < substringLength; i++) {
            current[i] = sc.next().charAt(0);
        }

        for (int index = 0; sc.hasNext(); index++) {
            for (int k = 0; k < index; k++) {
                boolean differ = false;
                compare = active.get(k);
                for (int j = 0; j < substringLength; j++) {
                    differ = differ || compare[j].compareTo(current[j]) != 0;
                }
                if (!differ)
                    throw new Exception("Match found for subset " + index);
            }
            active.add(current);
            prev = current;
            current = new Character[substringLength];
            for (int k = 1; k < substringLength; k++) {
                current[k - 1] = prev[k];
            }
            current[substringLength - 1] = sc.next().charAt(0);
        }

        System.out.println("Input is a valid version series.");
    }
}