#include <array>
#include <deque>
#include <iostream>
#include <vector>

#include <atcoder/modint>

using mint = atcoder::modint1000000007;

mint solve(std::array<std::deque<int>, 3> &target, int pos, int n) {
    if (n == 0) return 0;

    if (target[pos].size() and target[pos].front() == n) {
        target[pos].pop_front();
        return solve(target, pos, n - 1);
    }

    int target_pos = 0;
    for (int i = 0; i < 3; ++i) {
        if (target[i].size() and target[i].front() == n) {
            target_pos = i;
        }
    }
    target[target_pos].pop_front();
    return mint(2).pow(n - 1) + solve(target, 3 ^ pos ^ target_pos, n - 1);
}

int main() {
    int n;
    std::string s;
    std::cin >> n >> s;

    std::array<std::deque<int>, 3> target{};
    for (int i = 0; i < n; ++i) {
        target[s[i] - 'A'].push_front(i + 1);
    }
    std::cout << solve(target, 0, n).val() << '\n';
}