#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
using namespace std;
#define F first
#define S second
using LL = long long;
using i64 = long long;
using pii = pair<int,int>;
using pil = pair<int,i64>;
using pli = pair<i64,int>;
using pll = pair<i64,i64>;
#define str string
// #define mp make_pair
#define eb emplace_back
#define pb push_back
#define si(x) int(x.size())
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define LB lower_bound
#define UB upper_bound
#define i28 __int128
using u32 = unsigned;
using i64 = long long;
using u64 = unsigned long long;
#define one(X) memset((X), -1, sizeof((X)))
#define zero(X) memset((X), 0, sizeof((X)))
#define ar array


//for loop
#define rep1(n) for(LL i=0; i<(LL)(n); ++i)
#define rep2(i,n) for(LL i=0; i<(LL)(n); ++i)
#define rep3(i,a,b) for(LL i=(LL)(a); i<(LL)(b); ++i)
#define rep4(i,a,b,c) for(LL i=(LL)(a); i<(LL)(b); i+=(c))
#define cut4(a,b,c,d,e,...) e
#define rep(...) cut4(__VA_ARGS__,rep4,rep3,rep2,rep1)(__VA_ARGS__)
#define per1(n) for(LL i=((LL)n)-1; i>=0; --i)
#define per2(i,n) for(LL i=((LL)n)-1; i>=0; --i)
#define per3(i,a,b) for(LL i=((LL)a)-1; i>=(LL)(b); --i)
#define per4(i,a,b,c) for(LL i=((LL)a)-1; i>=(LL)(b); i-=(c))
#define per(...) cut4(__VA_ARGS__,per4,per3,per2,per1)(__VA_ARGS__)
#define rep_subset(i,s) for(LL i=(s); i>=0; i=(i==0?-1:(i-1)&(s)))

template<class t> using vc=vector<t>;
template<class t> using vvc=vc<vc<t>>;
template<class t> using vvvc = vc<vvc<t>>;

#define vv(type,name,n,...) \
    vector<vector<type>> name(n,vector<type>(__VA_ARGS__))
#define vvv(type,name,n,m,...) \
    vector<vector<vector<type>>> name(n,vector<vector<type>>(m,vector<type>(__VA_ARGS__)))
using vi = vc<int>;
using vl = vc<LL>;

template<typename T> inline bool chmax(T &a, T b) { return ((a < b) ? (a = b, true) : (false)); }
template<typename T> inline bool chmin(T &a, T b) { return ((a > b) ? (a = b, true) : (false)); }

//bit manipulation referenced from maroonrk
template<class T> int topbit(T t){return t==0?-1:63-__builtin_clzll(t);}
template<class T> int botbit(T t){return t==0?64:__builtin_ctzll(t);}
template<class T> int popcount(T t){return __builtin_popcountll(t);}


template<typename T> T gcd(T a,T b){ return b>0 ? gcd(b,a%b):a;}

template<typename T, typename TT> istream& operator >> (istream& i, pair<T,TT> &p){return i >> p.F >> p.S;}
template<typename T, typename TT> ostream& operator << (ostream& o, const pair<T,TT> &p){return o << p.F << ' ' << p.S;}

//cin vc<T>
template<typename T> istream& operator >> (istream& i, vc<T> &v){for(auto &x: v) i >> x; return i;}

//print 管理
template<typename T> void W(vector<vector<T>>& x){for(auto i: x){ for(auto j: i){cout << j << ' ';} cout << "\n";}}
template<typename T> void W(vector<T>& x){rep(si(x)) cout << x[i] << " \n"[i == si(x) - 1];}
template<typename T> void W(set<T>& x){for(auto i: x) cout << i << ' ';cout << "\n";}
template<typename T> void W(unordered_set<T>& x){for(auto i: x) cout << i << ' ';cout << "\n";}
template<typename T> void W(T && x) {cout << x << "\n";}
template<typename T, typename... S> void W(T && x, S&&... y) {cout << x << ' ';W(y...);}


template <class t> using mxheap = priority_queue<t>;
template <class t> using mnheap = priority_queue<t,vc<t>,greater<t>>;

std::mt19937_64 rng(std::chrono::steady_clock::now().time_since_epoch().count());

LL fpow(LL a, LL b, LL MOD) {
    LL res = 1;
    while(b) {
        if (b & 1) res = (res * a) % MOD;
        a = (a * a) % MOD;
        b >>= 1;
    }
    return res;
}

const int inf = 1e9;
const LL linf = 2e18;

void orZKYeh() {
    int n, k;
    cin >> n >> k;

    str s;
    cin >> s;

    const int K = 2501;
    vvv(bitset<K>, dp, n + 1, n + 1, n + 1);
    for (int i = 0; i <= n; i++) {
        dp[0][0][i][0] = 1;
    }
    for (int i = 0; i < n; i++) {
        if (s[i] == 'N' || s[i] == '?') {
            for (int N = 0; N <= i; N++) {
                for (int C = 0; C <= n - i; C++) {
                    dp[i + 1][N + 1][C] |= dp[i][N][C];
                }
            }
        }
        if (s[i] == 'A' || s[i] == '?') {
            for (int N = 0; N <= i; N++) {
                for (int C = 0; C <= n - i; C++) {
                    dp[i + 1][N][C] |= dp[i][N][C] << (N * C);
                }
            }
        }
        if (s[i] == 'C' || s[i] == '?') {
            for (int N = 0; N <= i; N++) {
                for (int C = 1; C <= n - i; C++) {
                    dp[i + 1][N][C - 1] |= dp[i][N][C];
                }
            }
        }
        if (s[i] == '?' || (s[i] != 'N' && s[i] != 'C' && s[i] != 'A')) {
            for (int N = 0; N <= i; N++) {
                for (int C = 0; C <= n - i; C++) {
                    dp[i + 1][N][C] |= dp[i][N][C];
                }
            }
        }
    }

    int N = -1;
    for (int i = 0; i <= n; i++) {
        if (dp[n][i][0][k]) {
            N = i;
        }
    }

    if (N == -1) {
        cout << -1 << '\n';
        return;
    }

    int C = 0;
    for (int i = n - 1; i >= 0; i--) {
        if ((s[i] == 'N' || s[i] == '?') && N > 0 && dp[i][N - 1][C][k]) {
            N--;
            s[i] = 'N';
        } else if ((s[i] == 'A' || s[i] == '?') && k >= N * C && dp[i][N][C][k - N * C]) {
            s[i] = 'A';
            k -= N * C;
        } else if ((s[i] == 'C' || s[i] == '?') && C + 1 <= n && dp[i][N][C + 1][k]) {
            C++;
            s[i] = 'C';
        } else if (s[i] == '?') {
            s[i] = 'Z';
        }
    }
    
    assert(k == 0);
    W(s);
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int t = 1;
    
    while(t--) {
        orZKYeh();
    }

}