#include <iostream>
#include <cstring>
#include <algorithm>
#include <limits.h>
#include <cmath>
#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)0

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
#define mid 2

/* ここからが本編 */
/*  */

/* pow(x,n)はx^nを返すよ！ */
ull pow(ull x,ull n) {
   ull res = 1;
   while(n > 0) {
      if(n&1) res = res * x;
      x = x * x;
      n >>= 1;
   }
   return res;
}
int main(void)
{
  int i,j,k,l;
  int test = 0;
  ull n;
  ull tmp;
  ull cnt = 1;
  cin >> n;
  tmp = n;
  while(tmp >= 26) {
    if(cnt != 1 && tmp == 26) break;
    tmp /= 26; cnt++;
  }
  tmp = pow((ull)26,cnt-1);
  if(n >= 26 && n%tmp == 0 && n/tmp == 2) {
    printf("%c",'A'-2+n/pow((ull)26,cnt-1));
    n -= (n/tmp-1)*tmp;
    cnt--;
  }
  else if(n >= 26){
    printf("%c",'A'-1+n/pow((ull)26,cnt-1));
    if(test) printf("\nn = %d\n",n);
    ull tmp = pow((ull)26,cnt-1);
    n -= n/tmp*tmp;
    cnt--;
  }
  while(cnt > 1) {
    ull tmp = pow((ull)26,cnt-1);
    if(test) printf("\nn = %d\n",n);
    if(n == 0) printf("A");
    else {
      printf("%c",'A'-1+n/tmp);
      n -= n/tmp*tmp;
    }
    cnt--;
  }
  printf("%c",'A'+n/pow((ull)26,cnt-1));
  puts("");
  return 0;
}