#include <stdio.h>

int main(){

  long long int N;
  char str[1024];
  scanf("%lld", &N);
  
  int i = 0;
  while(N>=0){
    if(i){
      str[i] = N%26 + 64;
    }
    else{
      str[i] = N%26 + 65;
    }
    N = N/26;
    if(N == 0){
      break;
    }
    i++;
  }

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

  printf("\n");

  return 0;
}