let str;
while(str = readline()){
let strArr = str.split('')
getMin(str,strArr)
}
function getMin(str,strArr){
let obj = {};
for(let v of strArr){
if(obj[v]){
obj[v]++;
}else{
obj[v] = 1;
}
}
//算出出现最少次数的数值是多少
let minNum = 20; //因为最多也就只能出现20次
for(let key in obj){
if(obj[key] < minNum){
minNum = obj[key];
}
}
let res = strArr;
for(let key in obj){
if(obj[key] == minNum){
res = res.filter((v)=>{
return v!=key;
})
}
}
console.log(res.join(''))
} 
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