#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint1000000007;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001

int main(){
	
	int n;
	cin>>n;
	
	vector<vector<int>> a(3);
	string s;
	cin>>s;
	
	rep(i,n){
		int t = s[i] - 'A';
		a[t].push_back(i);
	}
	
	vector<mint> dp(n+5);
	dp[1] = 1;
	for(int i=2;i<dp.size();i++){
		dp[i] = dp[i-1] * 2 + 1;
	}
	
	mint ans = 0;
	int cur = 0;
	for(int i=n-1;i>=0;i--){
		rep(j,3){
			if(binary_search(a[j].begin(),a[j].end(),i)){
				if(cur==j)break;
				ans += dp[i];
				ans++;
				cur = j ^ cur ^ 3;
				break;
			}
		}
	}
	
	cout<<ans.val()<<endl;
	
	
	
	return 0;
}