const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;

void async function () {
    // Write your code here
    while(line = await readline()){
        let tokens = line.split('').reverse();
        console.log([...new Set(tokens)].join(""))
    }
}()

先进行颠倒顺序reverse

然后去重

然后拼接打印