#include<bits/stdc++.h>
using namespace std;
string str = "";
int main(){
	int n;
	cin >> n;
	for(int i = 0 ;i < n ;i++){
		char c = 'A' + i;
		str = str + c + str;
	}
	cout << str;
	return 0;
}

就是不断翻折