#include<iostream>
using namespace std;
int N;
main()
{
	cin>>N;
	string ans="";
	for(char c='a';N;c++)
	{
		int L=1;
		while(L*(L+1)/2<=N)L++;
		N-=L*(L-1)/2;
		for(;--L;)ans+=c;
	}
	cout<<ans<<endl;
}