#include <bits/stdc++.h>
#include<iostream>
#include<iomanip>
#include<string>
#include<algorithm>
#include<vector>
#include<set>
#include<list>
#include<queue>
#include<math.h>
#include<bitset>
using ll = long long;
using namespace std;

int main()
{
    ll n;
    cin >> n;
    string s = "", a = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    while (n){
        int t;
        if (s.size() && n<26) n--;
        t = n%26;
        s += a[t];
        n /= 26;
    }
    reverse(s.begin(), s.end());
    cout << s << endl;
}