#include <iostream>
#include <math.h>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#define REP(i,n) for(int i=0;i<n;i++)
typedef long long ll;

using namespace std;
int kaijo(int n){
	int ans = 1;
	if (n != 0){
		for (int i = 0; i < n; i++){
			ans *= (n - i);
		}
	}
	else{
		ans = 1;
	}
	return ans;
}

int main(){
	string s;
	string s2;
	string str="a";
	int n;
	cin >> n;
	while (n != 1){
		if (n == (n / 2) * 2){
			n = n / 2;
			s = s+str;
		}
		else{
			n = n - 1;
			s = s + str;
			str[0] = str[0] + 1;
		}
	}
	//cout << s << endl;
	s2 = s;
	reverse(s.begin(), s.end());
	cout << s2 << "z" << s << endl;
	return 0;
}