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 obj = {};
// obj = {
// a: 2,
// b: 1,
// c: 1,
// d: 2
// }
line.split('').map((cell, index) => {
if (obj[cell]) {
obj[cell] += 1;
} else {
obj[cell] = 1;
}
});
let min = Math.min(...Object.values(obj));
const arr = [];
for (let key in obj) {
if (obj[key] === min) {
delete obj[key];
}
}
const brr = Object.keys(obj);
for (let k = 0; k < line.length; k++) {
if (brr.some((m) => line[k] === m)) {
arr.push(line[k])
}
}
console.log(arr.join(''));
}
}()