function MergSortEntry(arr){
    
   // console.log(arr)
    let tempArr = [];
    let i = MergeSort(arr, tempArr, 0, arr.length - 1)
    //console.log(arr)
    return i 
}
function MergeSort(arr, tempArr, leftStart, rightEnd ){
    
    let invCount = 0; 
    if( rightEnd > leftStart ){
        
      let mid =  parseInt( (leftStart + rightEnd) / 2 );
      invCount   += MergeSort(arr, tempArr, leftStart, mid);
      invCount   += MergeSort(arr, tempArr,  mid + 1, rightEnd);
      invCount   += MergeAndCount(arr, tempArr, leftStart, mid + 1, rightEnd);
    }
    return invCount;
}


function MergeAndCount(arr, tempArr, leftIdx, midIdx, rightIdx){
    
    let invCount    = 0;
    let leftNewIdx  = leftIdx // idx for left sub array
    let rightNewIdx = midIdx  // idx for right sub array
    let tempIdx     = leftIdx  // idx for temp array
    
    while ( ( leftNewIdx <= midIdx - 1) && ( rightNewIdx <= rightIdx ) ){
        
        if( arr[leftNewIdx] <= arr[rightNewIdx]){
            tempArr[tempIdx] = arr[leftNewIdx];
            leftNewIdx++;
        }else{
            tempArr[tempIdx] = arr[rightNewIdx];
            rightNewIdx++;
            invCount +=  (midIdx  - leftNewIdx);
           // console.log('--- invcount temp--', invCount +=  (midIdx  - leftNewIdx) )
        }
         
        tempIdx++; 
    }
    
    while( leftNewIdx <= midIdx - 1 ){
        tempArr[tempIdx] = arr[leftNewIdx];
        leftNewIdx++;
        tempIdx++; 
    }
    
    while( rightNewIdx <= rightIdx ){
        tempArr[tempIdx] = arr[rightNewIdx];
        rightNewIdx++;
        tempIdx++; 
    }
    
    for( var i = leftIdx; i <= rightIdx; i++){
        arr[i] = tempArr[i];
    }
    return invCount;
}




var a = [34, 203, 3, 746, 200, 984, 198, 764, 9];
var  b = [2,1,3,1,2]

//console.log( MergSortEntry(b));
//console.log( MergSortEntry(a));