#include <bits/stdc++.h>

using namespace std;

array<int, 3> get_next_cnt(array<int, 3> cnt, char c) {
    switch (c) {
        case 'N':
            ++cnt[0];
            break;
        case 'A':
            cnt[1] += cnt[0];
            break;
        case 'C':
            cnt[2] += cnt[1];
            break;
    }

    return cnt;
}

char back[40][41][401][2367];
bitset<2367> vis[40][41][401];

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, k;
    cin >> n >> k;

    string s;
    cin >> s;

    if (k > 2366) {
        cout << -1 << '\n';
        return 0;
    }

    queue<array<int, 3>> q;
    q.push({0, 0, 0});

    auto update = [&](int i, array<int, 3> cnt, char c) {
        auto& [x, y, z] = cnt;
        if (!vis[i][x][y][z]) {
            vis[i][x][y][z] = 1;
            back[i][x][y][z] = c;
            q.push({x, y, z});
        }
    };

    for (int i = 0; i < n; ++i) {
        int sz = size(q);
        while (sz--) {
            auto cnt = q.front();
            q.pop();

            for (char c : "NAC"s) {
                if (s[i] == '?' || s[i] == c) {
                    update(i, get_next_cnt(cnt, c), c);
                }
            }
            if (s[i] == '?') {
                update(i, cnt, 'B');
            }
            if (s[i] != '?') {
                update(i, get_next_cnt(cnt, s[i]), s[i]);
            }
        }
    }

    for (int x = 0; x <= 40; ++x) {
        for (int y = 0; y <= 400; ++y) {
            if (vis[n - 1][x][y][k]) {
                string ans(n, '#');
                for (int i = n - 1; i >= 0; --i) {
                    ans[i] = back[i][x][y][k];
                    switch (ans[i]) {
                        case 'N':
                            --x;
                            break;
                        case 'A':
                            y -= x;
                            break;
                        case 'C':
                            k -= y;
                            break;
                    }
                }

                cout << ans << '\n';
                return 0;
            }
        }
    }

    cout << -1 << '\n';
}