#include <bits/stdc++.h>
#include <iostream>
#include <math.h>
using namespace std;
int main() {
    int64_t N;
    cin >> N;
    string ans = "";
    do {
        ans += (char)('A' + (N % 26));
        N /= 26;
        N--;
    } while (N >= 0);

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