#pragma GCC optimize ( "O3" )
//#pragma GCC target ( "avx" )
#include <iostream>
#include <string>
#include <stdio.h>
#include <stdint.h>
#include <cassert>
using namespace std;

using ll = long long;

#define TYPE_OF( VAR ) remove_const<remove_reference<decltype( VAR )>::type >::type
#define UNTIE ios_base::sync_with_stdio( false ); cin.tie( nullptr ) 
#define CEXPR( LL , BOUND , VALUE ) constexpr const LL BOUND = VALUE 
#define CIN( LL , A ) LL A; cin >> A 
#define ASSERT( A , MIN , MAX ) assert( MIN <= A && A <= MAX ) 
#define CIN_ASSERT( A , MIN , MAX ) CIN( TYPE_OF( MAX ) , A ); ASSERT( A , MIN , MAX ) 
#define FOREQ( VAR , INITIAL , FINAL ) for( TYPE_OF( FINAL ) VAR = INITIAL ; VAR <= FINAL ; VAR ++ ) 
#define QUIT return 0 
#define RETURN( ANSWER ) cout << ( ANSWER ) << "\n"; QUIT 

// 入力フォーマットチェック用
// 余分な改行を許さない
#define CHECK_REDUNDANT_INPUT string VARIABLE_FOR_CHECK_REDUNDANT_INPUT = ""; cin >> VARIABLE_FOR_CHECK_REDUNDANT_INPUT; assert( VARIABLE_FOR_CHECK_REDUNDANT_INPUT == "" ); assert( ! cin );
// #define CHECK_REDUNDANT_INPUT string VARIABLE_FOR_CHECK_REDUNDANT_INPUT = ""; getline( cin , VARIABLE_FOR_CHECK_REDUNDANT_INPUT ); assert( VARIABLE_FOR_CHECK_REDUNDANT_INPUT == "" ); assert( ! cin );
// |N| <= BOUNDを満たすNをSから構築
#define STOI( S , N , BOUND ) TYPE_OF( BOUND ) N = 0; { bool VARIABLE_FOR_POSITIVITY_FOR_STOI = true;  assert( S != "" ); if( S.substr( 0 , 1 ) == "-" ){ VARIABLE_FOR_POSITIVITY_FOR_STOI = false; S = S.substr( 1 ); assert( S != "" ); } assert( S.substr( 0 , 1 ) != " " ); while( S == "" ? false : S.substr( 0 , 1 ) != " " ){ assert( N < BOUND / 10 ? true : N == BOUND / 10 && stoi( S.substr( 0 , 1 ) ) <= BOUND % 10 ); N = N * 10 + stoi( S.substr( 0 , 1 ) ); S = S.substr( 1 ); } if( ! VARIABLE_FOR_POSITIVITY_FOR_STOI ){ N *= -1; } if( S != "" ){ S = S.substr( 1 ); } } 
// 1行で入力される変数の個数が適切か確認（半角空白の個数+1を調べる）
#define COUNT_VARIABLE( S , VARIABLE_NUMBER ) { int size = S.size(); int count = 0; for( int i = 0 ; i < size ; i++ ){ if( S.substr( i , 1 ) == " " ){ count++; } } assert( count + 1 == VARIABLE_NUMBER ); } 

int main()
{
  UNTIE;
  CEXPR( ll , bound_N , 1000 );
  CIN_ASSERT( N , 1 , bound_N );
  CIN( string , S );
  // CHECK_REDUNDANT_INPUT;
  int i = S.size() - 1;
  string c[3] = { "A" , "B" , "C" };
  while( i >= 0 ? S.substr( i , 1 ) == c[0] : false ){
    i--;
  }
  if( i < 0 ){
    RETURN( 0 );
  }
  // n個の時にフラクタル端点への移動するターン数a(n)
  // a(0) = 0
  // a(n+1) = 2a(n) + 1
  // -> a(n) = 2^n - 1;
  ll a_plus[bound_N];
  ll power = 1;
  CEXPR( ll , P , 1000000007 );
  a_plus[0] = 1;
  FOREQ( j , 1 , i ){
    a_plus[j] = ( power *= 2 ) %= P;
  }
  ll answer = 0;
  string s;
  int d = 0;
  while( i >= 0 ){
    s = S.substr( i , 1 );
    // フラクタル上の最短経路を通る
    if( s != c[d] ){
      if( s == c[(++d)%=3] ){
	(++d)%=3;
      }
      answer += a_plus[i];
    }
    i--;
  }
  RETURN( answer % P );
}