#include <bits/stdc++.h>
using namespace std;
const long long INF = 9e15;
long long mod = 1000000007;
long long gcd(long long a, long long b) {
  if (b > a) {
    return gcd(b, a);
  }
  if (b == 0) {
    return a;
  }
  return gcd(b, a % b);
}
long long expo(long long a, long long b, long long mod) {
  long long res = 1;
  while (b > 0) {
    if (b & 1) res = (res * a) % mod;
    a = (a * a) % mod;
    b = b >> 1;
  }
  return res;
}
long long invprime(long long a, long long b) { return expo(a, b - 2, b); }
long long addmod(long long a, long long b, long long m) {
  a = a % m;
  b = b % m;
  return (((a + b) % m) + m) % m;
}
long long mulmod(long long a, long long b, long long m) {
  a = a % m;
  b = b % m;
  return (((a * b) % m) + m) % m;
}
long long submod(long long a, long long b, long long m) {
  a = a % m;
  b = b % m;
  return (((a - b) % m) + m) % m;
}
long long divmod(long long a, long long b, long long m) {
  a = a % m;
  b = b % m;
  return (mulmod(a, invprime(b, m), m) + m) % m;
}
vector<int> sieve(int n) {
  int* arr = new int[n + 1]();
  vector<int> vect;
  for (int i = 2; i <= n; i++)
    if (arr[i] == 0) {
      vect.push_back(i);
      for (int j = 2 * i; j <= n; j += i) arr[j] = 1;
    }
  return vect;
}
void google(int x) { cout << "Case #" << x << ": "; }
template <typename T>
void sort(vector<T>& v) {
  std::sort(v.begin(), v.end());
  return;
}
template <typename T>
void sortbig(vector<T>& v) {
  std::sort(v.begin(), v.end(), greater<T>());
  return;
}
template <typename T>
T max(vector<T>& v) {
  return *(max_element(v.begin(), v.end()));
}
template <typename T>
T min(vector<T>& v) {
  return *(min_element(v.begin(), v.end()));
}
template <typename T>
ostream& operator<<(ostream& stream, vector<T>& v) {
  for (T& x : v) stream << x << " ";
  return stream;
}
template <typename T>
istream& operator>>(istream& stream, vector<T>& v) {
  for (T& x : v) stream >> x;
  return stream;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  clock_t t1, t2;
  t1 = clock();
  int tc = 0, tt = 1;
  while (tc++ < tt) {
    string s;
    cin >> s;
    int n = s.length();
    unordered_set<int> ab, ba;
    for (int i = 0; i < n - 1; i++) {
      if (s[i] == 'A' && s[i + 1] == 'B') {
        for (int j = i + 2; j < n - 1; j++) {
          if (s[j] == 'B' && s[j + 1] == 'A') {
            cout << "YES" << '\n';
            return 0;
          }
        }
        break;
      }
    }
    for (int i = 0; i < n - 1; i++) {
      if (s[i] == 'B' && s[i + 1] == 'A') {
        for (int j = i + 2; j < n - 1; j++) {
          if (s[j] == 'A' && s[j + 1] == 'B') {
            cout << "YES" << '\n';
            return 0;
          }
        }
        break;
      }
    }
    cout << "NO" << '\n';
  }
  return 0;
}
