개발야옹

https://www.acmicpc.net/problem/1157

const fs = require('fs');
const input = fs.readFileSync('/dev/stdin').toString().trim().toUpperCase().split("");
const dic = {};

input.forEach((i) => {
    if(dic[i] === undefined) {
        dic[i] = 1;
    } else {
        dic[i] += 1;
    }
});

const keyList = Object.keys(dic);
const list = [];
let cnt = 0;
let maxKey = '';

keyList.forEach((key) => {
   list.push(dic[key]); 
});

let max = Math.max(...list);

keyList.forEach((key) => {
    if(dic[key] === max) {
        maxKey = key;
        cnt++;
    }
    if(cnt > 1) return false;
});

if(cnt > 1) console.log("?");
else console.log(maxKey);