const line = readline()
const arr = line.split("")
const data = {}
arr.forEach( item => {
if( data[item] ) {
data[item] += 1
}else {
data[item] = 1
}
})
let min = arr.length
Object.keys( data ).forEach( key => {
if( data[key] < min ) {
min = data[key]
}
})
const targetArr = []
Object.keys( data ).forEach( key => {
if( data[key] === min ) {
targetArr.push(key)
}
})
let str = line
targetArr.forEach( key => {
let reg = new RegExp(key, 'g');
str = str.replace( reg, "" )
})
console.log( str )

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