// inputに入力データ全体が入る
function Main(input) {
  const inputLines = input.split("\n");
  const line0 = inputLines[0];

  var n = parseInt(line0, 10);
  var result = "";

  const dogs = 1000000000000001;
  const abcs = "abcdefghijklmnopqrstuvwxyz";

  while (0 < n) {
    var m = n % 26;
    if (m === 0) {
      m = 26;
    }
    result = abcs.substr(m - 1, 1) + result;
    n = (n - m) / 26;
  }

  console.log(result);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
//Main("123456789");
