const main = input => {
  const num = Number(input);
  const ALPHA = "abcdefghijklmnopqrstuvwxyz".split("");
  const genIndices = (x, arr) => {
    const rem = (x - 1) % 26 + 1;
    const div = (x - rem) / 26;
    if (div === 0) {
      return [rem].concat(arr);
    }
    return genIndices(div, [rem].concat(arr));
  }
  const alphas = genIndices(num, []).map(i => ALPHA[i - 1]);
  console.log(alphas.join(""));
}

main(require("fs").readFileSync("/dev/stdin", "utf8"));