#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using pii = pair<int, int>;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define repr(i, n) for (int i = (int)(n - 1); i >= 0; --i)

using mint = modint1000000007;
int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n;
    string s;
    cin >> n >> s;
    mint ret = 0;
    char t = 'A';
    repr(i, n) {
        if (s[i] != t) {
            char c = 'A';
            ret += mint(2).pow(i);
            while (c == s[i] || c == t) c++;
            t = c;
        }
    }
    cout << ret.val() << endl;
    return 0;
}