#include "bits/stdc++.h"
using namespace std;
#define print(x) cout<<x<<endl;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define REP(i,a) for(int i=0;i<a;i++)
typedef long long ll;
typedef pair<int, int> PI;
typedef pair<int, PI> V;
typedef vector<int> VE;
const ll mod = 1000000007;

int main() {
  ll n;
  cin>>n;
  int i=1;
  char s[20];
  s[0]='A'+n%26;
  n/=26;
  while(n!=0){
    n--;
    s[i++]='A'+n%26;
    n/=26;
  }
  int m=i;
  for(int i=m;i>=0;i--)putchar(s[i]);
  cout<<endl;
  return 0;
}