#include <bits/stdc++.h>
#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <string>
#include <sstream>
#include <cmath>
#include <stack>
#include <queue>
#include <cctype>
#include <stdio.h>
#include <map>
#include <string.h>
#include <utility>

typedef long long ll;
using namespace std;

typedef pair<int, int> P;


int main() {

	ll n;
	cin >> n;

	string ans;

	while (n >= 0) {
		ans.push_back(n % 26 + 'A');
		n /= 26;
		n--;
	}

	reverse(ans.begin(),ans.end());
	cout<<ans<<endl;
	return 0;
}