#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <atcoder/modint>
 
using namespace std;
using i32 = int32_t;
using u32 = uint32_t;
using i64 = int64_t;
using u64 = uint64_t;
#define rep(i,n) for(int i=0; i<(int)(n); i++)
const i64 INF = 1001001001001001001;
 
using Modint = atcoder::modint1000000007;

int main(){
    int N; cin >> N;
    string S; cin >> S;
    S += "A";
    Modint ans = 0;
    for(int i=N-1; i>=0; i--){
        if(S[i] != S[i+1]){
            ans += Modint(2).pow(i);
            S[i] = S[i+1] ^ S[i] ^ 'A' ^ 'B' ^ 'C';
        }
    }
    cout << ans.val() << endl;
    return 0;
}
 
 
struct ios_do_not_sync{
    ios_do_not_sync(){
        std::ios::sync_with_stdio(false);
        std::cin.tie(nullptr);
    }
} ios_do_not_sync_instance;