#include <cstdio>
#include <cstdint>
#include <vector>
#include <string>
#include <algorithm>

int main() {
  uintmax_t N;
  scanf("%ju", &N);

  std::string res;

  do {
    res += 'A' + (N % 26);
    N /= 26;
  } while (N-- != 0);

  std::reverse(res.begin(), res.end());
  printf("%s\n", res.c_str());
}