#include <stdio.h>

int main(){

  long long int N;
  char str[1024];
  scanf("%lld", &N);
  
  int i = 0;

  if(N == 0){
    printf("A\n");
    return 0;
  }

  while(N >= 0){
    str[i] = N%26 + 65;
    N /= 26;
    N--;
    i++;
  }

  while(i > 0){
    printf("%c", str[i - 1]);
    i--;
  }

  printf("\n");

  return 0;
}