#include<iostream>
#include<algorithm>
using namespace std;
using lint=int64_t;

int main()
{
	lint N;
	string ans="";

	cin >> N;
	while(N>=0)
	{
		ans=(char)(N%26+'A')+ans;
		N/=26;
		N--;
	}

	cout << ans << endl;
	return 0;
}