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

#define int long long

typedef vector<int>vint;
typedef pair<int,int>pint;
typedef vector<pint>vpint;
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define all(v) (v).begin(),(v).end()
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
#define pb push_back
#define fi first
#define se second
template<typename A,typename B>inline void chmin(A &a,B b){if(a>b)a=b;}
template<typename A,typename B>inline void chmax(A &a,B b){if(a<b)a=b;}

signed main(){
    int N,D;
    cin>>N>>D;

    if(N>=D){
        cout<<string(D,'A')+string(N-D,'C')<<endl;
    }
    else{
        cout<<string(2*N-D,'A')+string(D-N,'B')<<endl;
    }
}