import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        // read n
        if (!sc.hasNextInt()) {
            System.out.println("Invalid input");
            return;
        }
        int n = sc.nextInt();

        if (n < 1 || n > 100) {
            System.out.println("Invalid input");
            return;
        }

        String[] words = new String[n];
        for (int i = 0; i < n; i++) {
            if (!sc.hasNext()) {
                System.out.println("Invalid input");
                return;
            }
            String word = sc.next();
            // check constraints: lowercase only, length 1–10
            if (!word.matches("[a-z]{1,10}")) {
                System.out.println("Invalid input");
                return;
            }
            words[i] = word;
        }

        int maxLen = -1, currLen = 1;
        for (int i = 1; i < n; i++) {
            if (!words[i].equals(words[i - 1])) {
                currLen++;
            } else {
                maxLen = Math.max(maxLen, currLen);
                currLen = 1;
            }
        }
        maxLen = Math.max(maxLen, currLen);

        // if maxLen < 2, no valid subsequence
        if (maxLen < 2) {
            System.out.println(-1);
        } else {
            System.out.println(maxLen);
        }
    }
}