计挑赛:在一个由小写英文字母(a-z)组成的字符串中，查找最长子串，其头尾字母相同，且中间不包含该头尾字母，并输出最左边的该类子串.

```java
import java.util.Scanner;

public class Main {

	public static void main(String args[]) {
		Scanner scan = new Scanner(System.in);
		String str = scan.next();
		char[] a = new char[str.length()];
		int max = 0, m = 0, n = 0;
		int flag = 0;
		for (int i = 0; i < str.length(); i++) {
			a[i] = str.charAt(i);
		}
		for (int i = 0; i < str.length(); i++) {
			for (int j = i + 1; j < str.length(); j++) {
				if (a[j - 1] == a[j] && max != 0) {
					flag++;
					break;

				}
				if (a[j] == a[i] && j - i + 1 > max) {
					max = j - i + 1;
					m = i;
					n = j;
					break;
				}
			}
		}
		System.out.println(flag);
		for (int i = m; i <= n; i++)

			System.out.print("" + a[i]);
	}
}