//Author: Kevin
#include<bits/stdc++.h>
//#pragma GCC optimize("O2")
using namespace std;
#define ll long long
#define ull unsigned ll
#define pb emplace_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
#define inf 0x3f3f3f3f
#define pii pair<int,int>
#define lb(v,x) (int)(lower_bound(ALL(v),x)-v.begin())
#define ub(v,x) (int)(upper_bound(ALL(v),x)-v.begin())
#define uni(v) v.resize(unique(ALL(v))-v.begin())
#define longer __int128_t
void die(string S){puts(S.c_str());exit(0);}
bitset<2504> bs[44][44][44];
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int n,x;
	cin>>n>>x;
	string s;
	cin>>s;
	for(int i=0;i<=n;i++)
		bs[0][0][i][0]=1;
	for(int i=0;i<n;i++)
		for(int a=0;a<=i;a++)
			for(int b=0;b<=n-i;b++)
			{
				if(s[i]=='N'||s[i]=='?')
					bs[i+1][a+1][b]|=bs[i][a][b];
				if(s[i]=='A'||s[i]=='?')
					bs[i+1][a][b]|=bs[i][a][b]<<(a*b);
				if(s[i]=='C'||s[i]=='?') if(b)
					bs[i+1][a][b-1]|=bs[i][a][b];
				if(s[i]!='N'&&s[i]!='A'&&s[i]!='C')
					bs[i+1][a][b]|=bs[i][a][b];
			}
	int a=-1,b=0,c=x;
	for(int i=0;i<=n;i++)
		if(bs[n][i][b][c])
			a=i;
	if(a==-1)
	{
		cout<<a<<endl;
		return 0;
	}
	string ans=s;
	for(int i=n-1;i>=0;i--)
		if(s[i]!='?')
		{
			if(s[i]=='N')
				a--;
			if(s[i]=='A')
				c-=a*b;
			if(s[i]=='C')
				b++;
		}
		else if(a&&bs[i][a-1][b][c])
		{
			s[i]='N';
			a--;
		}
		else if(c>=a*b&&bs[i][a][b][c-a*b])
		{
			s[i]='A';
			c-=a*b;
		}
		else if(bs[i][a][b+1][c])
		{
			s[i]='C';
			b++;
		}
		else
			s[i]='X';
	cout<<s<<endl;
	return 0;
}