function challenge(array,n){
    var sub = [];
    var count=0;
    for(var i = 0; i < array.length/2;i++){
        for(var j = 1; j < array.length;j++){
            if(array[i]+array[j]==n){
                sub[count] = [i,j];
                count++;
                //console.log("["+i+ ", " + j + "]");
            }
        }
    }
    return sub;
}

//driver code
var arr = [1, 3, 4, 5, 6, 8, 10, 11, 13];
var num = 14;
var ans = challenge(arr,num);
console.log(ans)