#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define rng(a) a.begin(),a.end()
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<P> vp;
#define dame { puts("-1"); return 0;}
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005


int main() {
    ll n;
    cin >> n;
    int keta = 1;
    ll p = 26;
    while(true){
        if(p <= n){
            n -= p;
            p *= 26;
            keta++;
        }else{
            int ans[keta];
            drep(i,keta){
                ans[i] = n % 26;
                n /= 26;
            }
            rep(i,keta){
                cout << (char)(ans[i] + 65);
            }
            cout << endl;
            return 0;
        }
    }
    return 0;
}