#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    long long n;
    cin >> n;

    string ret;
    do {
        ret = string(1, 'A' + n % 26) + ret;
        n /= 26;
    } while (n > 26);
    if (n > 0) ret = string(1, 'A' + n - 1) + ret;

    cout << ret << endl;
    return 0;
}