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 nums = line.split("");

      let reverseNums = nums.reverse();

      let result = new Set(reverseNums);
      let resultStr = '';
      result.forEach(item => {
        resultStr += item;
      })
      console.log(resultStr);
    }
}()