function main(lines) {
  let n = +lines[0];

  let res = '';
  while (n > 26) {
    res = String.fromCharCode(96 + n % 26) + res;
    n = Math.floor(n/26);
  }
  res = String.fromCharCode(96 + n) + res;
  
  console.log(res);
}


main( require("fs").readFileSync("/dev/stdin", "utf8").trim().split("\n") );



function splitN(s) {
  return s.split(' ').map(Number);
}