function Main(input) {
  var a = 0;
  var n = parseInt(input);
  if(n%2 === 1) {
    a = 2 * n;
  }
  else if(n%2 == 0) {
    a = n;
  }
  console.log(a)
  return 0;
}

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