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

int main(){
	srand((unsigned int)time(NULL));
	int n,m;
	cin>>m;//蒙m道题
	for(int i=0;i<m;i++){
		n=rand()%4+1;
		if(n==1) cout<<"A";
		else if(n==2) cout<<"B";
		else if(n==3) cout<<"C";
		else if(n==4) cout<<"D";
	}
	return 0;
}