#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cmath>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <sstream>
#include <string>
#define repd(i,a,b) for (int i=(a);i<(b);i++)
#define rep(i,n) repd(i,0,n)
#define var auto
#define mod 1000000007
#define inf 2147483647
#define nil -1
#define mp make_pair
typedef long long ll;
using namespace std;

template <typename T>
inline void output(T a, int p) {
    if(p){
        cout << fixed << setprecision(p)  << a << "\n";
    }
    else{
        cout << a << "\n";
    }
}
// end of template

ll power(ll n, int p){
    ll ret = 1;
    rep(i, p){
        ret *= n;
    }
    return ret;
}

int main() {
    cin.tie(0);
    // source code
    ll N;
    cin >> N;
    int p = 1;
    
    while (N - power(26, p) >= 0) {
        N -= power(26, p);
        p++;
    }
    vector<ll> ret(p);
    rep(i, p){
        ret[i] = (N / power(26, i)) % 26;
        ret[i]++;
    }
    reverse(ret.begin(), ret.end());
    rep(i, ret.size()){
        cout << char('A' + ret[i] - 1);
    }
    cout << endl;
    
    
    return 0;
}