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

using i32 = int32_t;
using i64 = int64_t;
#define i128 __int128_t
using u32 = uint32_t;
using u64 = uint64_t;
using f64 = long double;
// -------------------
con i32 MXN = 41;
con i32 MXK = 2501;

i32 n, k;
bool vis[MXN][MXN][MXN];
bitset<MXK> dp[MXN][MXN][MXN];
string fit, res;

void dps(i32 t, i32 i, i32 j) {
    if(vis[t][i][j]) return;
    vis[t][i][j] = true;
    bool all = fit[t]=='?';
    bool fgn = all || fit[t]=='N';
    bool fga = all || fit[t]=='A';
    bool fgc = all || fit[t]=='C';
    bool oth = !fgn && !fga && !fgc;

    if(fgn&&i<n) {
        dps(t+1, i+1, j);
        dp[t][i][j] |= dp[t+1][i+1][j];
    }
    if(fga) {
        dps(t+1, i, j);
        dp[t][i][j] |= dp[t+1][i][j] >> (i*j);
    }
    if(fgc&&j) {
        dps(t+1, i, j-1);
        dp[t][i][j] |= dp[t+1][i][j-1];
    }
    if(oth) {
        dps(t+1, i, j);
        dp[t][i][j] |= dp[t+1][i][j];
    }
}

void dfs(i32 t, i32 i, i32 j, i32 num) {
    if(t==n) return;
    bool all = fit[t]=='?';
    bool fgn = all || fit[t]=='N';
    bool fga = all || fit[t]=='A';
    bool fgc = all || fit[t]=='C';
    bool oth = !fgn && !fga && !fgc;

    if(fgn&&i<n) {
        if(dp[t+1][i+1][j][num]) {
            res[t] = 'N';
            dfs(t+1, i+1, j, num);
            return;
        }
    }
    if(fga&&num+(i*j)<=k) {
        if(dp[t+1][i][j][num+i*j]) {
            res[t] = 'A';
            dfs(t+1, i, j, num+i*j);
            return;
        }
    }
    if(fgc&&j) {
        if(dp[t+1][i][j-1][num]) {
            res[t] = 'C';
            dfs(t+1, i, j-1, num);
            return;
        }
    }

    if(oth) {
        res[t] = all?'B':fit[t];
        dfs(t+1, i, j, num);
        return;
    }
}

void solve() {
    for(i32 j=0; j<=n; ++j) {
        dps(0, 0, j);
        if(dp[0][0][j][0]) {
            dfs(0, 0, j, 0);
            cout << res;
            return;
        }
    }
    cout << "-1";
}

void pre() {
    cin >> n >> k;
    cin >> fit; res = fit;
    for(i32 i=0; i<=n; ++i) {
        dp[n][i][0].set(k);
        fill(vis[n][i], vis[n][i]+n+1, true);
    }
}

void aft() {
    cout << '\n';
}

u32 _t = 1;
void init() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    // cin >> _t;
}

int main() {
    init();
    for(u32 i=1; i<=_t;) {
        pre(); solve();
        ++i<=_t?aft():exit(0);
    }
}