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()){
const a = [];
const b = line.split('').reverse();
for (let i = 0; i < b.length; i++){
if (a.indexOf(b[i]) === -1){
a.push(b[i])
}
}
console.log(a.join(''))
}
}()