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

#define RREP(i,s,e) for (i = e-1; i >= s; i--)
#define rrep(i,n) RREP(i,0,n)
#define REP(i,s,e) for (i = s; i < e; i++)
#define rep(i,n) REP(i,0,n)
#define INF 1e8

int main() {
    long long n;
    cin >> n;
    string ans;
    n++;
    while (n > 0) {
        n--;
        ans.push_back(n % 26 + 'A');
        n /= 26;
    }
    reverse(ans.begin(),ans.end());
    cout << ans << endl;
    return 0;
}