#include <bits/stdc++.h>
using namespace std;
int main(int argc, char** argv) {
  char s[12];
  int cnt = 0;
  long long n;
  scanf("%lld", &n);
  while (n > 0) {
    if (n == 26LL) {
      s[cnt++] = 'z';
      break;
    }
    int r = n % 26LL;
    s[cnt++] = r == 0 ? 'z' : r + 'a' - 1;
    n /= 26LL;
  }
  for (int i = cnt - 1; i >= 0; i--) putchar(s[i]);
  putchar('\n');
  return 0;
}
