https://programmers.co.kr/learn/courses/30/lessons/12916
function solution(s){
s=s.toLowerCase();
let pc=0, yc=0;
for(let i=0; i<s.length; i++){
if(s[i]==='p') pc++;
else if(s[i]==='y') yc++;
}
if(pc===yc) return true;
else return false;
}