약수의 개수와 덧셈

function counter(input){
    let cnt = 1;
    
    for(let i = 1 ; i <= Math.floor(input /2) ; i++){
        if( input % i === 0){
            cnt++;
        }
    }   
    return cnt ;
}


function solution(left, right) {
    var answer = 0;
    
    for(let i = left ; i<= right ; i ++){
        
        var tt = counter(i)    
        
        if(tt % 2 === 0 ) answer += i;
        else answer -= i;
    }
    
    return answer;
    
}