题解 | #汽水瓶#

const readline = require("readline");

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

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