#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main() {
    long long n; cin >> n;
    auto to_str = [](long long n) {
        string res;
        while (n--) res += char('A' + n % 26), n /= 26;
        return res;
    };
    cout << to_str(n + 1) << endl;
    return 0;
}