#include<bits/stdc++.h>
using namespace std;

const int N=200003;
int n,a,e,l,r,v[N];
char p[N];
int main()
{
	int T;cin>>T;
	while(T--)
	{
		cin>>n>>a>>e;int k=0;
		for(int i=1;i<=2*n;i++)
		{
			cin>>p[i];
			if(p[i]=='A')k++;
		}
		l=abs(k-a);r=a+k;
		if(l<=e&&e<=r&&(e-l)%2==0&&(r-l)%2==0)
		{
			int w=min(a,k)-(e-l)/2,z=0;
			for(int i=1;i<=2*n;i++)
			{
				if(p[i]=='A')
				{
					if(z<w)z++,v[i]=1;
				}
				else
				{
					if(z>=w&&z<a)z++,v[i]=1;
				}
			}
			for(int i=1;i<=2*n;i++)
			{
				if(v[i]==0)cout<<'B';
				else cout<<'A';
				v[i]=0;
			}
			cout<<endl;
		}
		else cout<<-1<<endl;
	}
	return 0;
}