#include <bits/stdc++.h>
#include <stdio.h>
#include <iostream>
#include <string>

using namespace std;

int main()
{
    freopen ("Input.txt", "r", stdin);
    freopen ("Output.txt", "w", stdout);
    int n,a,b,c;
    cin>>n>>a>>b>>c;
    int k=0;
    for(int i=0;i<a-1;i+=2){
        cout<<"AB";
        k++;
    }
    if(a%2==1){
        cout<<"A";
        k++;
    }
    for(int i=0;i<b-1;i+=2){
        cout<<"cd";
        k++;
    }
    if(a%2==1){
        cout<<"c";
        k++;
    }
    for(int i=0;i<c-1;i+=2){
        cout<<"10";
        k++;
    }
    if(a%2==1){
        cout<<"1";
        k++;
    }
    return 0;
}