#include <stdio.h>
int main(){
  long long int N;
  int i=0;
  char buf[10];
  scanf("%lld",&N);
  N++;
  while(N>0){
    N--;
    buf[i]=(N%26)+65;
    N=N/26;
    i++;
  }
  i--;
  while(i>=0){
    printf("%c",buf[i]);
    i--;
  }
  printf("\n");
  return 0;
}