#include<bitset>
#include<cstdio>
#include<algorithm>
template<typename T>void read(T &x){
	x=0;bool f=0;char ch=getchar();
	for(;ch<'0'||ch>'9';ch=getchar())if(ch=='-')f=1;
	for(;ch>='0'&&ch<='9';ch=getchar())x=(x<<1)+(x<<3)+(ch^48);
	if(f)x=-x;
}
void write(char x){putchar(x);}
template<typename T>void write(T x){
	if(x<0)putchar('-'),x=-x;
	char stk[24];int cnt=0;
	do stk[++cnt]=x%10+48,x/=10;while(x);
	for(;cnt;)putchar(stk[cnt--]);
}
template<typename T,typename ...Args>void read(T &x,Args &...args){read(x);read(args...);}
template<typename T,typename ...Args>void write(T x,Args ...args){write(x);write(args...);}
template<typename T>T min(T x,T y){return x<y?x:y;}
template<typename T>T max(T x,T y){return x>y?x:y;}
int n,m;std::bitset<2504>dp[44][44][44];char a[44],b[44];
signed main(){
	read(n,m);scanf("%s",a+1);
	for(int i=0;i<=n;++i)dp[0][0][i].set(0);
	for(int i=1;i<=n;++i)for(int j=0;j<=i;++j)for(int k=0;k<=n-i;++k){
		if((a[i]=='N'||a[i]=='?')&&j)dp[i][j][k]|=dp[i-1][j-1][k];
		if(a[i]=='C'||a[i]=='?')dp[i][j][k]|=dp[i-1][j][k+1];
		if(a[i]=='A'||a[i]=='?')dp[i][j][k]|=dp[i-1][j][k]<<j*k;
		if(a[i]!='N'&&a[i]!='C'&&a[i]!='A')dp[i][j][k]|=dp[i-1][j][k];
	}
	int p=0;
	for(;p<=n&&!dp[n][p][0][m];++p);
	if(p>n)return puts("-1"),0;
	for(int i=n,j=p,k=0,l=m;i;--i)
		if(a[i]=='N'||(a[i]=='?'&&j&&dp[i-1][j-1][k][l]))j--,b[i]='N';
		else if(a[i]=='C'||(a[i]=='?'&&dp[i-1][j][k+1][l]))k++,b[i]='C';
		else if(a[i]=='A'||(a[i]=='?'&&l>=j*k&&dp[i-1][j][k][l-j*k]))l-=j*k,b[i]='A';
		else b[i]=(a[i]=='?'?'S':a[i]);
	printf("%s\n",b+1);
	return 0;
}