((arr) => {
 arr.sort((a, b) => a - b);
 let i = 0;
 let max = null;
 let res = 0;
 for (; i < arr.length && arr[i] < 0; ++i) {
   if (max == null) max = arr[i];
   else {
     res += max * arr[i];
     max = null;
   }
 }
 for (; i < arr.length && arr[i] === 0; ++i) {
   if (max != null) max = null;
 }
 if (max != null) res += max;
 for (let j = arr.length; i <= j; --j) {
   if (max == null) {
     max = arr[j];
   } else {
     res += max * arr[j];
     max = null;
   }
 }
 if (max != null) res += max;

 return res;
})([-5,0,1,2,3,4,5]);