#include <stdio.h>
#include <iostream>
#include <vector>
#include <queue>
#include <stack>
#include <algorithm>

#pragma GCC optimize("O2")

using ll = long long int;
const int INF = (1<<30);
const ll INFLL = (1ll<<60);
const ll MOD = (ll)(1e9+7);

#define l_ength size

void mul_mod(ll& a, ll b){
	a *= b;
	a %= MOD;
}

void add_mod(ll& a, ll b){
	a = (a<MOD)?a:(a-MOD);
	b = (b<MOD)?b:(b-MOD);
	a += b;
	a = (a<MOD)?a:(a-MOD);
}

std::string s;
ll sp[1111];

int main(void){
	int n,i;
	char t = 'A';
	ll ans = 0ll;
	std::cin >> n;
	for(i=1; i<=n; ++i){
		sp[i] = sp[i-1];
		mul_mod(sp[i],2ll); 
		add_mod(sp[i],1ll);
	}
	std::cin >> s;
	for(i=n-1; i>=0; --i){
		if(s[i] == t){
			continue;
		}
		t = 'A'+'B'+'C'-s[i]-t;
		add_mod(ans,1ll);
		add_mod(ans,sp[i]);
	}
	std::cout << ans << std::endl;
	return 0;
}