#include<bits/stdc++.h>
using namespace std;
#define int long long
signed main()
{
	int n,k;
	string ans="";
	cin>>n;
	while(n)
	{
		k=n%26;
		if(!k)
		{
			k=26;
			n--;
		}
		ans=(char)('a'+k-1)+ans;
		n/=26;
	}
	cout<<ans;
	return 0;
}