#include <bits/stdc++.h>
using namespace std;
string str;
long long dp[150][150];
long long from_b[150][150];
long long calc(int len, string after, char st_char) {
  for (int i = 2; i < len; i++) {
    if (after[i] == 'B') {
      dp[i]['B'] = dp[i - 1]['B'];
    } else {
      if (after[i - 1] == 'A') {
        dp[i]['A'] = dp[i - 1]['A'] + dp[i - 1]['B'];
      } else {
        dp[i]['B'] = dp[i - 2]['A'] + dp[i - 2]['B'];
        dp[i]['A'] = dp[i - 1]['A'] + dp[i - 1]['B'];
      }
    }
    printf("dp[%d][%c] = %lld dp[%d][%c] = %lld\n", i, 'A', dp[i]['A'], i, 'B',
           dp[i]['B']);
  }
  return dp[len][st_char];
}
int main() {
  cin >> str;
  int st = str.find('B');
  if (st == -1) {
    cout << 1 << endl;
    return 0;
  }
  int len = str.length();
  string after = str.substr(st, len - st) + str.substr(0, st);
  string pre2 = after.substr(0, 2);
  memset(dp, 0, sizeof(dp));
  if (pre2 == "AA") {
    dp[0]['A'] = 1;
    dp[1]['A'] = 1;
    dp[0]['B'] = 0;
    dp[1]['B'] = 0;
  } else if (pre2 == "AB") {
    dp[0]['A'] = 1;
    dp[0]['B'] = 0;
    dp[1]['A'] = 0;
    dp[1]['B'] = 0;
  } else if (pre2 == "BA") {
    dp[0]['A'] = 0;
    dp[0]['B'] = 1;
    from_b[0]['B'] = 1;
    dp[1]['A'] = 1;
    from_b[1]['A'] = 1;
    dp[1]['B'] = 1;
  } else if (pre2 == "BB") {
    dp[0]['A'] = 0;
    dp[0]['B'] = 1;
    from_b[0]['B'] = 1;
    dp[1]['A'] = 0;
    dp[1]['B'] = 1;
    from_b[1]['B'] = 1;
  }
  for (int i = 2; i < len; i++) {
    if (after[i] == 'B') {
      dp[i]['B'] = dp[i - 1]['B'];
      from_b[i]['B'] = from_b[i - 1]['B'];
    } else {
      if (after[i - 1] == 'A') {
        dp[i]['A'] = dp[i - 1]['A'] + dp[i - 1]['B'];
        from_b[i]['A'] = from_b[i - 1]['A'] + from_b[i - 1]['B'];
      } else {
        dp[i]['B'] = dp[i - 2]['A'] + dp[i - 2]['B'];
        dp[i]['A'] = dp[i - 1]['A'] + dp[i - 1]['B'];
        from_b[i]['B'] = from_b[i - 2]['A'] + from_b[i - 2]['B'];
        from_b[i]['A'] = from_b[i - 1]['A'] + from_b[i - 1]['B'];
      }
    }
  }
  cout << dp[len - 1]['A'] + dp[len - 1]['B'] - from_b[len - 1]['A'] << endl;
}
