/*
            _           __                _      _____ _____ _____ 
  ___ _   _| |__   ___ / _|_ __ ___  __ _| | __ |___  |___  |___  |
 / __| | | | '_ \ / _ \ |_| '__/ _ \/ _` | |/ /    / /   / /   / / 
| (__| |_| | |_) |  __/  _| | |  __/ (_| |   <    / /   / /   / /  
 \___|\__,_|_.__/ \___|_| |_|  \___|\__,_|_|\_\  /_/   /_/   /_/   

*/
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
typedef long long ll ;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<int> vl;
typedef vector<pll> vpll;
typedef unordered_map <ll,ll> umap ; 
//#pragma GCC optimize "trapv"
#define loop(i,a,b) for(ll i=a ;i<b;i++)
#define For(i,n) for(int i=0;i<(ll)n;i++)
#define Rev(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,n) for(int i=1;i<=n;++i)
#define F first
#define S second
#define pb push_back
#define em emplace_back
#define all(v) (v).begin(),(v).end()                                                              
#define mems(x, y) memset(x, y, sizeof(x))
#define sz(v) (v).size()
#define mp(a,b) make_pair(a,b)
#define pf(n) {cout<<n<<"\n" ; return ;}
#define po(n) cout << n <<"\n " 
#define pff(n) cout << n << " " ; 
#define ar array
#define endl "\n" 
#define PI acos(-1) 
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
//#ifndef ONLINE_JUDGE
//#ifndef LOCAL
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
//#else
//#define debug(x...)
//#endif
#define int ll 
template<class T> using oset =tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update> ;
long const M=1e9+7;
const long mxN =1e5+2 ;
const ll INF =1e18;
string X="abcdefghijklmnopqrstuvwxyz";
ll x=26ll ;
ll P(ll b,ll p){
  ll r=1 ;
  for(;p;p/=2ll,b=b*b)if(p&1ll)r=b*r ;
  return r ;
}
void solve(){ 
  ll n ;
  cin >>  n ;
  ll s=0ll,c=1ll ;
  for(;;){
    if(s+P(x,c)>=n)
      break ;
    s+=P(x,c);
    c++ ;
  }
  n-=s ;
  string ans ="" ;
  while(c>0){
    int v = P(x,c-1ll) ;
    ll k=(n+v-1ll)/v ;
    ans+=X[k-1ll] ;
    --c ;
    n-=v*(k-1ll);
    // debug(c,n) ;
  }
  cout << ans << endl ;
  
  
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  //cout << setprecision(20) << fixed ;
  solve() ;
  // ll t ; cin >> t ; while(t--)solve() ;
	return 0;
}


Measured memory_bytes: 3668