#include <bits/stdc++.h>
using namespace std;

#define sz(x) (int)x.size()

const int N = 1e6 + 200;
const int M = 1e6;

int dp[21][21][101][301], pdp[21][21][101][301];
int pd[21][21][101][301], ppd[21][21][101][301];

int n, k;
string s, a, b;

int get(char c) {
    if (c == '?') return -1;
    if (c == 'N') return 0;
    if (c == 'A') return 1;
    if (c == 'C') return 2;
    return 3;
}

void print(int x, int y, int z, int X, int Y, int Z) {
    string A, B;
    for (int i = sz(a); i >= 1; --i) {
        int c = pdp[i][x][y][z];
        int nx = x - (c == 0), ny = y - x * (c == 1), nz = z - y * (c == 2);
        x = nx, y = ny, z = nz;
        A += (c == 0 ? "N" : (c == 1 ? "A" : (c == 2 ? "C" : "Z")));
    }
    reverse(A.begin(), A.end());
    x = X, y = Y, z = Z;
    for (int i = sz(b); i >= 1; --i) {
        int c = ppd[i][x][y][z];
        int nx = x - (c == 2), ny = y - x * (c == 1), nz = z - y * (c == 0);
        x = nx, y = ny, z = nz;
        B += (c == 0 ? "N" : (c == 1 ? "A" : (c == 2 ? "C" : "Z")));
    }
    A += B;
    for (int i = 0; i < n; ++i) {
        if (A[i] == 'Z') A[i] = s[i];
        if (A[i] == '?') A[i] = 'Z';
    }
    cout << A << '\n';
    return;
}

int main() {
    ios_base::sync_with_stdio(0), cin.tie(0);
    cin >> n >> k;
    cin >> s;
    a = s.substr(0, n / 2);
    b = s.substr(n / 2, n);
    reverse(b.begin(), b.end());
    dp[0][0][0][0] = 1;
    pd[0][0][0][0] = 1;
    for (int i = 1; i <= sz(a); ++i) {
        for (int c = 0; c < 4; ++c) {
            if (get(a[i - 1]) != -1) 
                c = get(a[i - 1]);
            for (int x = 0; x <= 20; ++x) {
                for (int y = 0; y <= 100; ++y) {
                    for (int z = 0; z <= 300; ++z) {
                        if (dp[i - 1][x][y][z]) {
                            dp[i][x + (c == 0)][y + x * (c == 1)][z + y * (c == 2)] = 1;
                            pdp[i][x + (c == 0)][y + x * (c == 1)][z + y * (c == 2)] = c;
                        }
                    }
                }
            }
            if (get(a[i - 1]) != -1) 
                break;
        }
    }
    for (int i = 1; i <= sz(b); ++i) {
        for (int c = 0; c < 4; ++c) {
            if (get(b[i - 1]) != -1) 
                c = get(b[i - 1]);
            for (int x = 0; x <= 20; ++x) {
                for (int y = 0; y <= 100; ++y) {
                    for (int z = 0; z <= 300; ++z) {
                        if (pd[i - 1][x][y][z]) {
                            pd[i][x + (c == 2)][y + x * (c == 1)][z + y * (c == 0)] = 1;
                            ppd[i][x + (c == 2)][y + x * (c == 1)][z + y * (c == 0)] = c;
                        }
                    }
                }
            }
            if (get(b[i - 1]) != -1) 
                break;
        }
    }
    for (int x = 0; x <= 20; ++x) {
        for (int y = 0; y <= 100; ++y) {
            for (int z = 0; z <= 300; ++z) {
                if (dp[sz(a)][x][y][z] == 0) continue;
                if (z > k) break;
                for (int X = 0; X <= 20; ++X) {
                    if (z + y * X > k) break;
                    for (int Y = 0; Y <= 100; ++Y) {
                        if (z + y * X + x * Y > k) break;
                        int Z = k - (z + y * X + x * Y);
                        if (Z > 300) continue;
                        if (pd[sz(b)][X][Y][Z] == 0) continue;
                        print(x, y, z, X, Y, Z);
                        return 0;
                    }
                }
            }
        }
    }
    cout << -1 << '\n';

}