function Main(input) {
  const N = input.trim();
  var radix = 'zabcdefghijklmnopqrstuvwxy'.split('');
  var tmp = 26;
  var i = 1;
  while (N >= tmp) {
    tmp = tmp + tmp * 26;
    i++;
  }
  var tmp2 = [];
  for (j = 1; j <= i; j++) {
    tmp2.unshift(radix[Math.floor((N / Math.pow(26, j-1))) % 26]);
  }
  var result = tmp2.join('');
  console.log(result);
}

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