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

#define FORR(i,b,e) for(int i=(b);i<(int)(e);++i)
#define FOR(i,e) FORR(i,0,e)
#define ALL(c) begin(c), end(c)
#define dump(var) cerr << #var ": " << var << "\n"
#define dumpc(con) for(auto& e: con) cerr << e << " "; cerr<<"\n"

using namespace std;

typedef long long ll;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    const int base = 26;
    ll N;
    cin >> N;
    string alpha_n = "";
    if (N < base) {
        cout << (char)('A' + N) << endl;
    }
    else {
        while (N > 0) {
            if (N < base) {
                alpha_n.insert(0, 1, 'A' + N % base - 1);
            }
            else {
                alpha_n.insert(0, 1, 'A' + N % base);
            }
            N /= base;
        }
        cout << alpha_n << endl;
    }
    return 0;
}