#include <bits/stdc++.h>
//#include <boost/multiprecision/cpp_int.hpp>
using namespace std;
//using Graph = vector<vector<edge>>;
using dou =long double;
string yes="yes";
string Yes="Yes";
string YES="YES";
string no="no";
string No="No";
string NO="NO";

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
typedef long long ll;
typedef pair<int,int> P;
typedef pair<ll,ll> PL;
const ll mod = 1000000007;
//const ll mod = 998244353;
struct mint {
  ll x; // typedef long long ll;
  mint(ll x=0):x((x%mod+mod)%mod){}
  mint operator-() const { return mint(-x);}
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod-a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) { (x *= a.x) %= mod; return *this;}
  mint operator+(const mint a) const { return mint(*this) += a;}
  mint operator-(const mint a) const { return mint(*this) -= a;}
  mint operator*(const mint a) const { return mint(*this) *= a;}
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t>>1);
    a *= a;
    if (t&1) a *= *this;
    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod-2);}
  mint& operator/=(const mint a) { return *this *= a.inv();}
  mint operator/(const mint a) const { return mint(*this) /= a;}
};
istream& operator>>(istream& is, const mint& a) { return is >> a.x;}
ostream& operator<<(ostream& os, const mint& a) { return os << a.x;}




#define rep(i, n)         for(ll i = 0; i < (int)(n); i++)
#define brep(n)           for(int bit=0;bit<(1<<n);bit++)
#define erep(i,container) for (auto &i : container)
#define irep(i, n)        for(int i = n-1; i >= (int)0; i--)
#define rrep(i,m,n) for(ll i = m; i < (ll)(n); i++)
#define reprep(i,j,h,w) rep(i,h)rep(j,w)
#define all(x) (x).begin(),(x).end()
#define VEC(type,name,n) std::vector<type> name(n);rep(i,n)std::cin >> name[i];
#define pb push_back
#define pf push_front
#define query int qq;std::cin >> qq;rep(qqq,qq)
#define lb lower_bound
#define ub upper_bound
#define fi first
#define se second
#define itn int
#define mp make_pair
#define sum(a) accumulate(all(a),0ll)
#define keta fixed<<setprecision
#define vout(a) erep(qxqxqx,a)std::cout << qxqxqx << ' ';std::cout  << std::endl;
#define vvector(name,typ,m,n,a)vector<vector<typ> > name(m,vector<typ> (n,a))
//#define vvector(name,typ,m,n)vector<vector<typ> > name(m,vector<typ> (n))
#define vvvector(name,t,l,m,n,a) vector<vector<vector<t> > > name(l, vector<vector<t> >(m, vector<t>(n,a)));
#define vvvvector(name,t,k,l,m,n,a) vector<vector<vector<vector<t> > > > name(k,vector<vector<vector<t> > >(l, vector<vector<t> >(m, vector<t>(n,a)) ));
#define case std::cout <<"Case #" <<qqq+1<<": "
#define res resize
#define as assign
#define ffor for(;;)
#define ppri(a,b) std::cout << a<<" "<<b << std::endl
#define pppri(a,b,c) std::cout << a<<" "<<b <<" "<< c<<std::endl
#define aall(x,n) (x).begin(),(x).begin()+(n)
#define ssum(a) accumulate(a,0ll) 


//typedef long long T;
ll ceil(ll a,ll b){
    return ((a+b-1)/b);
}
const int INF = 2000000000;
const ll INF64 =3223372036854775807ll;
//const ll INF64 = 9223372036854775807ll;
//const ll INF64 = 9223372036854775ll;
const ll MOD = 1000000007ll;
const dou pi=3.141592653589793;

//tuple<hoge,huga,foo> tのget関数はget<i>(t)
//resizeはメンバ関数

class Radix { //n進数に変換
// Radix rと宣言してからr.to(a,b)で変換
//pをq進数にする
private:
  const char* s;
  int a[100000];
public:
  Radix(const char* s = "abcdefghijklmnopqrstuvwxyz") : s(s) {
    int i;    for(i = 0; s[i]; ++i)

      a[(int)s[i]] = i;
  }
  std::string to(long long p, int q) {
    int i;
    if(!p)
      return "a";
    char t[64000] = { };
    for(i = 62000; p; --i) {
      t[i] = s[p % q];
      p /= q;
    }
    return std::string(t + i + 1);
  }
  std::string to(const std::string& t, int p, int q) {
    return to(to(t, p), q);
  }
  long long to(const std::string& t, int p) {
    int i;
    long long sm = a[(int)t[0]];
    for(i = 1; i < (int)t.length(); ++i)
      sm = sm * p + a[(int)t[i]];
    return sm;
  }
};
int main(){
    ll n;
    std::cin >> n;
    std::vector<ll> d;
    d.pb(1);
    ffor{
        d.pb(d[d.size()-1]*26);
        if(d[d.size()-1]>3670344486987776ll)break;
    }
    std::vector<ll> ddd(d.size());
    ddd[0]=d[0];
    rrep(i,1,d.size()){
        ddd[i]=ddd[i-1]+d[i];
    }
    reverse(all(d));
    reverse(all(ddd));
//    vout(ddd);
    Radix r;
    erep(i,ddd){
        if(i<=n){
            n-=i;
            string s=r.to(n,26);
            ll du=i;
            int cn=0;
            while(du){
                cn++;
                du/=26;
            }
            while(s.size()!=cn)s.insert(s.begin(),'a');
            std::cout << s << std::endl;
            exit(0);
        }
        
    }
}



Measured memory_bytes: 3672