PassWord

const readline= require('readline');
const rl= readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    terminal:false
});

const userInput=[];

rl.on("line", (data)=>{
    userInput.push(data);
});

rl.on('close', ()=>{
    console.log(firstNotRepeatingCharacter(userInput[0]));
})




function firstNotRepeatingCharacter(s) {
    for (let i = 0; i < s.length; i++) {
        if(s.indexOf(s.charAt(i)) == s.lastIndexOf(s.charAt(i))) {
            return s.charAt(i)
        }
    }
    return     
}