#include <iostream>
#include <vector>
#include <set>
#include <deque>
#include <map>
#include <iomanip>
#include <queue>
#include <stack>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <utility>
using namespace std;
int ky[8] = {-1,1,-2,2,-2,2,-1,1}; 
int kx[8] = {-2,-2,-1,-1,1,1,2,2};
int dy[4] = {-1,0,1,0};
int dx[4] = {0,1,0,-1};
int ddy[8] = {-1,0,1,-1,1,-1,0,1};
int ddx[8] = {-1,-1,-1,0,0,1,1,1};
typedef long long ll;
#define pi pair
#define MP make_pair
#define PB push_back
#define F first
#define S second
#define rep1(i,a,b) for(int i = a; i < b; i++)
#define rep2(i,a,b) for(int i = a; i <= b; i++) 
#define INF 999999999999
const double PI = acos(-1.0); 
ll n;
ll num;
ll cnt;

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    //freopen("input.txt","r",stdin);
    //freopen("output.txt","w",stdout);
    cin >> n;
    num = 26;
    cnt = 1;
    while(n > num){
        n -= num;
        num *= 26;
        cnt++;
    }

    string ans(cnt, '0');
    --n;
    for(int i = cnt - 1; i >= 0; i--){
        ans[i] = (n % 26) + 'a';
        n /= 26;
    }
    cout << ans;
    return 0;  
}
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define all(a) a.begin(), a.end()
#define pb push_back
#define mp make_pair
typedef long long ll;
typedef pair<ll,ll> P;
typedef pair<ll,int> pli;
typedef pair<int,int> pii;
#define rep(i,a,b) for(ll i=a ; i<b ; i++)
#define qrep(que, ite) for(auto ite=begin(que) ; ite!=end(que) ; ite++)
const int max_n = 1e5;
const ll mod = 1e9+7;
const ll INF = 1e17;
const int inf = 1e5;
typedef long double ld;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
ll gcd(ll a, ll b) { return a ? gcd(b%a, a) : b; }
int dx[4] = {0,0,1,-1};
int dy[4] = {1,-1,0,0};
struct UnionFind {
    vector<int> par;

    UnionFind(int n) : par(n, -1) { }
    void init(int n) { par.assign(n, -1); }

    int root(int x) {
        if (par[x] < 0) return x;
        else return par[x] = root(par[x]);
    }

    bool issame(int x, int y) {
        return root(x) == root(y);
    }

    bool merge(int x, int y) {
        x = root(x); y = root(y);
        if (x == y) return false;
        if (par[x] > par[y]) swap(x, y); // merge technique
        par[x] += par[y];
        par[y] = x;
        return true;
    }

    int size(int x) {
        return -par[root(x)];
    }
};
struct SegmentTree{
  int N;
  vector<int> node;
  public :
    void intit(vector<int>v){
      int sz = v.size();
      N=1;
      while(N<sz) N*=2;
      node.resize(N);
      for(int i=0 ; i<sz ; i++) node[i+N-1] = v[i];
      for(int i=N-2 ; i>=0 ; i--) node[i] = min(node[i*2+1], node[i*2+2]);
    }
    void update(int x, int val){
      x += N-1;
      node[x+N-1] = val;
      while(x>0){
        x = (x-1)/2;
        node[x] = min(node[x*2+1], node[x*2+2]);
      }
    }
    int getmin(int a, int b, int k, int l, int r){
      if(b<=l || r<=a) return inf;
      else if(a<=l && r<=b) return node[k];
      else{
        int vl = getmin(a, b, 2*k+1, l, (l+r)/2);
        int vr = getmin(a, b, 2*k+2, (l+r)/2, r);
        return min(vl, vr);
      }
    }
};
vector<ll> divisor(ll n){
  vector<ll> res;
  for(ll i=1; i*i<=n ; i++){
    while(n%i==0){
      ++res[i];
      n /= i;
    }
  }
  if(n!=1) res[n]=1;
  return res;
}
int main(){
  ll n; cin >> n;
  ll k = n;
  int cnt = 1;
  while(true){
    ll now = pow(26, cnt);
    if(k - now > 0){
        k -= now;
        cnt++;
    }else{
        break;
    }
  }
  
  string ans = "";  
  k--;
  for(int i=cnt-1 ; i>=0 ; i--){
      ll now = pow(26, i);
      ll st = k / now;
      for(char c='a' ; c<='z' ; c++){
          if(c - 'a' == st){
              ans += c;
          }
      }
      k -= now * st;
  }
  cout << ans << endl;
  return 0;
}   