#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef complex<double> P;
typedef pair<int,int> pii;
#define REP(i,n) for(ll i=0;i<n;++i)
#define REPR(i,n) for(ll i=1;i<n;++i)
#define FOR(i,a,b) for(ll i=a;i<b;++i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define MOD (ll)(1e9+7)
#define ADD(a,b) a=((a)+(b))%MOD
#define FIX(a) ((a)%MOD+MOD)%MOD

int main(){
  ll n;
  cin>>n;
  string res = "";
  ll t = n;
  int len = 0;
  ll sum = 0;
  ll c = 26;
  while(t){
    ++len;
    sum += c;
    if(t<sum)break;
    c *= 26;
  }
  t=n;
  while(c/=26){
    t -= c;
  }
  if(n==0)len=1;
  ++t;
  REP(i,len){
    res = (char)(t%26+'A') + res;
    t/=26;
  }
  cout << res << endl;
  return 0;
}