46. 1157(단어 공부)

let input = require('fs').readFileSync('/dev/stdin').toString().split();

let str = input[0].toUpperCase();
let T = Array.from(new Set(str));
let max = 0;
let result = '';

for(let i = 0; i < T.length-1; i++){
    
    let N = str.match(new RegExp(T[i], "g")).length;
   
    if(max < N){
        max = N;
        result = T[i];
    }
    else if(max == N){
        result = '?';
    }
    
}
console.log(result);