#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)

typedef long long ll;

int main()
{
	ll N; cin >> N; N++;

	string ans = "";
	while (0 < N)
	{
		N--;
		ans += char('A' + N % 26);
		N /= 26;
	}

	cout << ans << endl;
}