#include <bits/stdc++.h>
#ifdef LOCAL
#include <debug.hpp>
#else
#define debug(...) void(0)
#endif

template <class T> std::istream& operator>>(std::istream& is, std::vector<T>& v) {
    for (auto& e : v) {
        is >> e;
    }
    return is;
}

template <class T> std::ostream& operator<<(std::ostream& os, const std::vector<T>& v) {
    for (std::string_view sep = ""; const auto& e : v) {
        os << std::exchange(sep, " ") << e;
    }
    return os;
}

template <class T, class U = T> bool chmin(T& x, U&& y) {
    return y < x and (x = std::forward<U>(y), true);
}

template <class T, class U = T> bool chmax(T& x, U&& y) {
    return x < y and (x = std::forward<U>(y), true);
}

template <class T> void mkuni(std::vector<T>& v) {
    std::ranges::sort(v);
    auto result = std::ranges::unique(v);
    v.erase(result.begin(), result.end());
}

template <class T> int lwb(const std::vector<T>& v, const T& x) {
    return std::distance(v.begin(), std::ranges::lower_bound(v, x));
}

using ll = long long;

using namespace std;

const int MAX_N = 40, MAX_NA = 20 * 20, MAX_K = 2510;
bitset<MAX_K> dp[MAX_N + 1][MAX_N + 1][MAX_NA + 1];
const string NAC = "NAC";

bool ok(char c, int i) {
    if (i < 3) return c == NAC[i] or c == '?';
    for (int i = 0; i < 3; i++) {
        if (c == NAC[i]) {
            return false;
        }
    }
    return true;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);
    int n, K;
    string S;
    cin >> n >> K >> S;

    dp[0][0][0][0] = 1;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= i; j++) {
            for (int k = 0; k <= j * (i - j); k++) {
                auto& val = dp[i][j][k];
                if (ok(S[i], 0) and j + 1 <= MAX_N) dp[i + 1][j + 1][k] |= val;
                if (ok(S[i], 1) and k + j <= MAX_NA) dp[i + 1][j][k + j] |= val;
                if (ok(S[i], 2)) dp[i + 1][j][k] |= val << k;
                if (ok(S[i], 3)) dp[i + 1][j][k] |= val;
            }
        }
    }

    int x = -1, y = -1;
    for (int j = 0; j <= MAX_N; j++) {
        for (int k = 0; k <= MAX_NA; k++) {
            if (dp[n][j][k][K]) {
                x = j, y = k;
            }
        }
    }
    if (x == -1) {
        cout << -1 << '\n';
        return 0;
    }
    string ans = "";
    for (int i = n - 1; i >= 0; i--) {
        if (ok(S[i], 0) and x - 1 >= 0 and dp[i][x - 1][y][K]) {
            x--;
            ans += NAC[0];
        } else if (ok(S[i], 1) and y - x >= 0 and dp[i][x][y - x][K]) {
            y -= x;
            ans += NAC[1];
        } else if (ok(S[i], 2) and K - y >= 0 and dp[i][x][y][K - y]) {
            K -= y;
            ans += NAC[2];
        } else if (ok(S[i], 3) and dp[i][x][y][K]) {
            ans += S[i] == '?' ? 'O' : S[i];
        } else {
            assert(false);
        }
    }
    ranges::reverse(ans);

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