#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();
#define rd(v) long v=0;{long _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}
#define rd_signed(v) long v=0;{long _c,_s;_s=*rp=='-'&&++rp;while(_c=*rp++-48,_c>=0)v=v*10+_c;v=_s?-v:v;}

char wbuf[1<<25];

#define rep(v,e) for(long v=0;v<e;++v)
#define rep3(v,s,e) for(long v=s;v<e;++v)

unsigned a[200000];
unsigned x[200000];

void indirect_radix_sort_aux(unsigned*x,unsigned*y,int n){
	int c[256];
	for(int i=0;i<256;++i){
		c[i]=0;
	}
	for(int i=0;i<n;++i){
		++c[a[i]&255];
	}
	int t=0;
	for(int i=0;i<256;++i){
		int u=c[i];
		c[i]=t;
		t+=u;
	}
	for(int i=0;i<n;++i){
		y[c[a[x[i]]&255]++]=x[i];
		a[x[i]]>>=8;
	}
}

void indirect_radix_sort(unsigned*x,int n){
	static unsigned y[200000];
	indirect_radix_sort_aux(x,y,n);
	indirect_radix_sort_aux(y,x,n);
	indirect_radix_sort_aux(x,y,n);
	indirect_radix_sort_aux(y,x,n);
}

main(){
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);
	rd(n);
	rd(k);
	rep(i,n){
		rd_signed(ai);
		a[i]=ai+(1u<<31);
	}
	rep(i,n){
		rd_signed(bi);
		a[i]-=bi;
	}
	rep(i,n){
		x[i]=i;
	}
	indirect_radix_sort(x,n);
	if(k*2<n){
		rep(i,n){
			wbuf[i]='B';
		}
		rep3(i,n-k,n){
			wbuf[x[i]]='A';
		}
	}else{
		rep(i,n){
			wbuf[i]='A';
		}
		rep(i,n-k){
			wbuf[x[i]]='B';
		}
	}
	wbuf[n]='\n';
	write(1,wbuf,n+1);
	_exit(0);
}