package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	var input = bufio.NewScanner(os.Stdin)
	var output byte
	for input.Scan() {
		line := input.Text()

		output = firstUniqChar(line)
		fmt.Println(string(output))
	}
}

func firstUniqChar(s string) byte {
	var record = [26]int{}
	for i := 0; i < len(s); i++ {
		var key = s[i] - 'a'
		record[key]++
	}
	for i := 0; i < len(s); i++ {
		var key = s[i] - 'a'
		if record[key] == 1 {
			return s[i]
		}
	}

	return ' '
}