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

#define ll long long
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
#define ld long double
#define forn(low,high,i) for(i = low; i < high; i++)
#define forrev(high,low,i) for(i = high; i >= low; i--)
#define all(v) v.begin(),v.end()
#define decimal_digits cout << fixed << setprecision(15);

string to_string(string s) { return '"' + s + '"';}
string to_string(char s) { return string(1, s);}
string to_string(const char* s) { return to_string((string) s);}
string to_string(bool b) { return (b ? "true" : "false");}
template <typename A> string to_string(A);
template <typename A, typename B>string to_string(pair<A, B> p) {return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";}
template <typename A> string to_string(A v) {bool f = 1; string r = "{"; for (const auto &x : v) {if (!f)r += ", "; f = 0; r += to_string(x);} return r + "}";}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {cerr << " " << to_string(H); debug_out(T...);}
#define pr(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

const int inf = 1e9;
const long long INF = 1e18;
const int mod = 1e9 + 7;
const int bit32 = log2(inf) + 3;
const int bit64 = log2(INF) + 3;

inline int add(long long a, long long b){a += b; if(a >= mod) a -= mod; return a;}
inline int sub(long long a, long long b){a -= b; if(a < 0) a += mod; return a;}
inline int mul(long long a, long long b){a %= mod; b %= mod; return (int)((long long) a * b % mod);}
inline int modexpo(long long a, long long b){int res = 1; while(b > 0){ if(b & 1) res = mul(res, a); a = mul(a, a); b /= 2;} return res;}
inline int divide(long long a, long long b){return mul(a, modexpo(b, mod - 2));}
inline int inv(long long a){return modexpo(a, mod - 2);}

clock_t time_p = clock();

void ktj(){
  time_p = clock() - time_p;
  cerr << "Time elapsed : " << (float)(time_p)/CLOCKS_PER_SEC << "\n";
}

void pre(){ // Reset each global variable (esp. for graphs)
  
}

const long long N = 1000000000000001;

void solve(){
  vector<char> a;
  for(char c = 'a'; c <= 'z'; c++){
    a.push_back(c);
  }
  long long n; cin >> n;
  string s = "";
  vector<long long> layer;
  long long sum = 0, mul = 26;
  while(sum <= N){
    layer.push_back(sum + mul - 1); 
    sum += mul; mul *= 26;
  }

  int digits = lower_bound(all(layer), n - 1) - layer.begin() + 1;

  mul = 1;
  long long sub = 0;
  for(int i = 1; i <= digits; i++){
    sub += mul; mul *= 26;
  }
  n -= sub;
  for(int i = 1; i <= digits; i++)
    s += 'a';
  mul /= 26;
  digits--;
  while(n and digits >= 0){
    long long pos = n / mul;
    s[digits] = 'a' + ((s[digits] - 'a') + pos);
    n -= mul * pos;
    mul /= 26;
    digits--;
  }
  reverse(all(s));
  cout << s << '\n';
}


#define GOOGLE 0
#define MULTIPLE_TC 0

int32_t main(){
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);cout.tie(NULL); 

  pre();

  int t = 1, T;
  if(MULTIPLE_TC)
    cin >> t;

  for(T = 1; T <= t; T++){
    if(GOOGLE)
      cout << "Case #" << T << ": ";
    solve();
  }

  ktj();
}

Measured memory_bytes: 3812