function main(input) {
  let N = parseInt(input.split("\n"), 10);
  let alphabet = "abcdefghijklmnopqrstuvwhyz";
  let result = "";

  while (0 < N) {
    let M = N % 26;
    if (M === 0) {
      M = 26;
    }
    result = alphabet.substr(M - 1, 1) + result;
    N = (N - M) / 26;
  }

  console.log(result);
}
main(require("fs").readFileSync("/dev/stdin", "utf8"));