#include "bits/stdc++.h"
using namespace std;


/* macro */
#define rep(i,a,b) for(int i=a;i<b;i++)
#define revrep(i,a,b) for(int i = a; i > b; i--)
#define int long long
#define exist(s,e) ((s).find(e)!=(s).end())
#define all(v) (v).begin(), (v).end()
#define each(s,itr) for(auto (itr) = s.begin(); (itr) != s.end(); (itr)++)
#define sum(v) accumulate(all(v), (0LL))


/* alias */
template<class T> using vec = vector<T>;
typedef vector<int> vi;
typedef pair<int, int> pi;


/* constant */
const int inf = 100100100100100100;
const int mod = 1e9;
int dx[8]={1,0,-1,0,-1,1,-1,1};
int dy[8]={0,1,0,-1,-1,-1,1,1};
string alphabet = "abcdefghijklmnopqrstuvwxyz";


/* io_method */
int input(){int tmp;cin >> tmp;return tmp;}
string raw_input(){string tmp;cin >> tmp;return tmp;}
string readline(){string s;getline(cin, s);return s;}
template<class T> void printx(T n){cout << n;}
template<class T, class U> void printx(pair<T, U> p){cout << "(" << p.first << "," << p.second << ")";}
template<class T> void printx(vector<T> v){cout << "{";rep(i,0,v.size()){printx(v[i]);if(i != v.size()-1)printx(",");}cout << "}";}
template<class T> void print(T n){printx(n);cout << endl;}
template<class T> void print(set<T> s){cout << "{";each(s, e){if(e != s.begin()) printx(",");printx(*e);}cout << "}" << endl;}
template<class T, class U> void print(map<T, U> mp){cout << "{";each(mp, e){cout << "(" << e -> first << "," << e -> second << ")";}cout << "}" << endl;}


/* general_method */
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }




/* main */
int n,m;
char arr[100][100];
int dp[100][100];

int dfs(int x, int y){
    if(arr[y][x] == '#' or y < 0 or n <= y or x < 0 or m <= x) return 1;
    if(dp[y][x] != 0) return dp[y][x];
    if(dfs(x + 1, y) == -1) return dp[y][x] = 1;
    if(dfs(x, y + 1) == -1) return dp[y][x] = 1;
    if(dfs(x + 1, y + 1) == -1) return dp[y][x] = 1;
    return dp[y][x] = -1;
}

signed main(){

    cin.tie(0);
    ios::sync_with_stdio(false);

    int n = input();
    if(n == 0){
        print("A");
        return 0;
    }

    vi arr;

    while(n){
        arr.push_back(n % 26);

        n /= 26;
        if(!n && arr.size() > 1) arr.back() -= 1;
    }

    reverse(all(arr));

    string s = "";

    rep(i,0,arr.size()){
        s.push_back(alphabet[arr[i]]);
    }
    
    transform(s.begin(), s.end(), s.begin() , ::toupper);
    print(s);





    




    
    



    
    



 
    
    


    

    
   
    













}