#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<int, int> PII;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
#define MOD 1000000007
#define INF (1LL<<25)     //33554432
#define PI 3.14159265359
#define EPS 1e-12
//#define int ll

//二分累乗法 xのe乗
ll binpow(ll x, ll e)
{
  ll a = 1, p = x;

  while(e > 0) {
    if(e%2 == 0) {p = (p*p); e /= 2;}
    else {a = (a*p); e--;}
  }

  return a;
}

signed main(void)
{
  ll n;
  cin >> n;

  ll a = 26, cnt = 1;
  string ans = "";
  while(true) {
    if(n < a) {
      for(ll i = cnt; i > 0; --i) {
        ll tmp = binpow(26, i-1);
        ans += n/tmp + 'A';
        n %= tmp;
      }
      break;
    }
    n -= a;
    a *= 26;
    cnt++;
  }

  cout << ans << endl;
  return 0;
}