#include <iostream>
#include <algorithm>

using namespace std;

long long N;

int main() {
    scanf("%lld", &N);
    
    if (N == 0) cout << "A";
    else {
        N ++;
        string res;
        while (N > 0) {
            N -- ;
            int mod = N % 26;
            res.push_back(mod + 'A');
            N /= 26;
        }
        reverse(res.begin(), res.end());
        cout << res;
    }
    return 0;
}