function test(n) {
  var result = []
  do {
    var code = ((n) % 26) + 65;
    result.unshift(String.fromCharCode(code));
    n = Math.floor(n / 26) - 1;
  } while (n >= 0);
  return (result.join(''))
}
function Main(input) {
  var input = input
    .toString()
    .split('\n')[0];
  var N = parseInt(input)
  console.log(test(N))
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));