题解 | #汽水瓶#

const readline = require("readline");

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
});
rl.on("line", function (line) {
  fn(+line);
});

const fn = (num: number) => {
  let res = 0;
  let n = num;
  if (num < 1) {
    return res;
  }
  while (n > 2) {
    res += Math.floor(n / 3);
    n = Math.floor(n / 3) + (n % 3);
  }
  if (n > 1) {
    res += 1;
  }
  console.log(res);
};