#include <bits/stdc++.h>
//#define int long long
#define fi first
#define se second 
#define pb push_back
#define ott(i, l, r) for (int i = (l); i <= (r); i ++)
#define tto(i, l, r) for (int i = (r); i >= (l); i --)
using namespace std;
typedef long long ll;
typedef long double ld;
int read () {
	int x = 0; bool f = false; char c = getchar ();
	while (!isdigit (c)) f |= (c == '-'), c = getchar ();
	while (isdigit (c)) x = (x << 3) + (x << 1) + (c ^ 48), c = getchar ();
	return f ? -x : x;
}
const int N = 41, K = 2501, mod = 1e9 + 7;
int n, k;
char s[N], ans[N];
bitset <K> f[N][N][N * N];
void dfs (int x, int a, int b, int c) {
    if (f[x][a][b][c]) return ; f[x][a][b][c] = true;
    if (c < k && b + c > k) return ;
    if (x == n + 1) {
        if (c == k) {
            printf ("%s\n", ans + 1);
            exit (0);
        }
        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);
    return ;
}
int main () {
    n = read (), k = read (); scanf ("%s", s + 1);
    dfs (1, 0, 0, 0); puts("-1");
    return 0;
}