#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1e5+999;
ll n,m,a[N],b[N];
multiset<ll> ms1,ms2;
multiset<ll>::iterator it;
bool judge(ll lim){
	ll l,r,mid,bl,br,bmid,cnt0;
	l=r=mid=bl=br=bmid=cnt0=0;
	ms1.clear(); ms2.clear();
	for(int i=1;i<=n;i++){
		if(a[i]-b[i]>0){
			ms2.insert(a[i]-b[i]);
		}
		else if(a[i]-b[i]==0){
			cnt0++;
		}
		else{
			ms1.insert(a[i]-b[i]);
			mid++;
			bmid+=a[i]-b[i];
		}
		br+=a[i]-b[i];
		r++;
		bl+=b[i]; bmid+=b[i]; br+=b[i];
		if(bmid<0){
			ll bn=bmid;
			if(bl<=0){
				bl=0;
				cnt0+=ms1.size();
				mid-=ms1.size();
				ms1.clear();
			}
			else{
				while(bn<0){
					it=ms1.end(); it--;
					if(bn-(*it)<=0){
						bn-=(*it);
						ms1.erase(it);
						mid--; cnt0++;
					}
					else{
						ll v=*it;
						ms1.erase(it);
						ms1.insert(v-bn);
						bn=0;
					}
				}
			}
			if(br<=0){
				br=0;
				cnt0+=ms2.size();
				ms2.clear();
			}
			else{
				bn=bmid;
				while(bn<0){
					it=ms2.begin();
					if(bn+(*it)<=0){
						bn+=(*it);
						ms2.erase(it);
						cnt0++;
					}
					else{
						ll v=*it;
						ms2.erase(it);
						ms2.insert(v+bn);
						bn=0;
					}
				}
			}
			bmid=0;
		}
		while(bl>lim){
			if(ms1.empty()) return false;
			bl+=*(ms1.begin());
			l++; ms1.erase(ms1.begin());
		}
		while(br>lim){
			if(ms2.empty()) return false;
			it=ms2.end(); it--;
			br-=(*it); r--; ms2.erase(it);
		}
	}
	if(l>m||r<m) return false;
	return true;
}
multiset<pair<ll,int> > Ms1,Ms2;
multiset<pair<ll,int> >::iterator It;
vector<int> z;
bool vis[N];
void solve(ll lim){
	ll l,r,mid,bl,br,bmid,cnt0;
	l=r=mid=bl=br=bmid=cnt0=0;
	for(int i=1;i<=n;i++){
		if(a[i]-b[i]>0){
			Ms2.insert(make_pair(a[i]-b[i],i));
		}
		else if(a[i]-b[i]==0){
			cnt0++;
			z.push_back(i);
		}
		else{
			Ms1.insert(make_pair(a[i]-b[i],i));
			mid++;
			bmid+=a[i]-b[i];
		}
		br+=a[i]-b[i];
		r++;
		bl+=b[i]; bmid+=b[i]; br+=b[i];
		if(bmid<0){
			ll bn=bmid;
			if(bl<=0){
				bl=0;
				mid-=Ms1.size();
				for(It=Ms1.begin();It!=Ms1.end();It++)
					z.push_back((*It).second),cnt0++;
				Ms1.clear();
			}
			else{
				while(bn<0){
					It=Ms1.end(); It--;
					if(bn-(*It).first<=0){
						bn-=(*It).first;
						z.push_back((*It).second);
						Ms1.erase(It);
						mid--; cnt0++;
					}
					else{
						ll v=(*It).first; int id=(*It).second;
						Ms1.erase(It);
						Ms1.insert(make_pair(v-bn,id));
						bn=0;
					}
				}
			}
			if(br<=0){
				br=0;
				for(It=Ms2.begin();It!=Ms2.end();It++)
					z.push_back((*It).second),cnt0++;
				Ms2.clear();
			}
			else{
				bn=bmid;
				while(bn<0){
					It=Ms2.begin();
					if(bn+(*It).first<=0){
						bn+=(*It).first;
						z.push_back((*It).second);
						Ms2.erase(It);
						cnt0++;
					}
					else{
						ll v=(*It).first; ll id=(*It).second;
						Ms2.erase(It);
						Ms2.insert(make_pair(v+bn,id));
						bn=0;
					}
				}
			}
			bmid=0;
		}
		while(bl>lim){
			bl+=(*Ms1.begin()).first;
			vis[(*Ms1.begin()).second]=1;
			l++; Ms1.erase(Ms1.begin());
		}
		while(br>lim){
			It=Ms2.end(); It--;
			br-=(*It).first; r--; Ms2.erase(It);
		}
	}
	while(l!=m){
		if(!Ms1.empty()){
			It=Ms1.begin();
			vis[(*It).second]=1;
			Ms1.erase(It);
		}
		else if(cnt0){
			cnt0--;
			vis[z.back()]=1;
			z.pop_back(); 
		}
		else{
			It=Ms2.begin();
			vis[(*It).second]=1;
			Ms2.erase(It);
		}
		l++;
	}
	for(int i=1;i<=n;i++)
		if(vis[i]) cout<<"A";
		else cout<<"B";
	return;
}
int main(){
	std::ios::sync_with_stdio(false);
	cin.tie(0);
	cin>>n>>m;
	for(int i=1;i<=n;i++) cin>>a[i];
	for(int i=1;i<=n;i++) cin>>b[i];
	ll l=0,r=1e14,mid,re=1e14;
	while(l<=r){
		mid=(l+r>>1);
		if(judge(mid)) re=mid,r=mid-1;
		else l=mid+1;
	}
	cout<<re<<endl;
	solve(re);
	return 0;
}