#include <bits/stdc++.h>
using namespace std;
#define rep(i,l,r) for (int i = (l); i <= (r); i++)
#define per(i,r,l) for (int i = (r); i >= (l); i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
#define maxn(a, b) a = max(a, b)
#define minn(a, b) a = min(a, b)
typedef vector<int> VI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
const ll mod = 998244353;
mt19937 gen(random_device{}());
ll rp(ll a,ll b) {ll res=1%mod;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}

const int N = 40;
const int K = 2514;
int n, k;
char s[N], ans[N];

void dfs(int x, int a, int b, int c) {
    if (x > n) {
        if (c == k) {
            printf("%s\n", ans + 1);
            exit(0);
        }
        return ;
    }
    if (c < k && b + c > k) return ;

    ans[x] = s[x];
    if (s[x] == 'N') {
        dfs(x + 1, a + 1, b, c);
    } else if (s[x] == 'A') {
        dfs(x + 1, a, b + a, c);
    } else if (s[x] == 'C') {
        dfs(x + 1, a, b, c + b);
    } else if (s[x] == '?') {
        ans[x] = 'S'; dfs(x + 1, a, b, c);
        ans[x] = 'N'; dfs(x + 1, a + 1, b, c);
        ans[x] = 'A'; dfs(x + 1, a, b + a, c);
        ans[x] = 'C'; dfs(x + 1, a, b, c + b);
    } else {
        dfs(x + 1, a, b, c);
    }
}

int main() {
    scanf("%d%d", &n, &k);
    scanf("%s", s + 1);
    dfs(1, 0, 0, 0);
    puts("-1");
    return 0;
}