#include <iostream>
#include <vector>

typedef long long dlong;

int main(int argc, char const* argv[]) {
    dlong n;
    std::cin >> n;

    std::vector<dlong> ans;

    for (;;) {
        ans.insert(ans.begin(), n%26);
        n /= 26;
        if (n == 0) break;
        n--;
    }

    for (const auto& var : ans) {
        std::cout << (char)('A' + var);
    }
    std::cout << std::endl;
    return 0;
}