function main(input) {
  var n = parseInt(input,10);
  var result = "";
  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"));
