http://codeforces.com/contest/550/problem/A

#include <iostream>
#include <cstring>

using namespace std;
const int XL = 3;
const int XXL = 1000*100;
int main()
{
    int k = 0;
    char a[XL]{"AB"};
    char b[XL]{"BA"};

    char t[XXL];
    cin >> t;

    int n = strlen(t);




        for (int j = 0; j< n-1; j++)
        {
            if (a[0] == t[j] && a[1] == t[j+1])
            {
                k++;
                t[j] = '0';
                t[j+1] = '0';
                break;//AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
            }
        }





        for (int j = 0; j < n-1; j++)
        {
            if (b[0] == t[j] && b[1] == t[j+1])
            {
                k++;
                break;//AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
            }
        }



        if (k >= 2)
        {
            cout << "YES";
        }

        else
        {
            cout << "NO";
        }


}