func missingNumbers(arr: [Int], brr: [Int]) -> [Int] {
    
    var storageArr = Array(repeating: 0, count: 10001)
    var resultArr: [Int] = []
    
    for i in 0..<arr.count {
        storageArr[arr[i]] -= 1 
    }
    for i in 0..<brr.count {
        storageArr[brr[i]] += 1 
    }

    for i in 0..<storageArr.count {
        if storageArr[i] > 0 {
            resultArr.append(i)
        }
    }
    
    return resultArr
}