#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repp(i, n) rep(i, 0, n)
#define repb(i, a, b) for(int i = a; i >= b; i--)
#define all(a) a.begin(), a.end()
#define int long long
using namespace std;

signed main(){
    int n;
    cin >> n;
    string s = "";
    while(1){
        int tmp = n % 26;
        n /= 26;
        if(n == 0 && s != "") tmp--;
        s += (char)('A' + tmp);
        if(n == 0) break;
    }
    reverse(all(s));
    cout << s << endl;
}