int erfen(int arr[],int key,int n)
    {
        int low=0,high=n-1;
        while(low<=high)
        {
            int mid=(low+high)/2;
            if(arr[mid]<key)
            {
                low=mid+1;
            }
            if(arr[mid]==key)
            {
                return mid;
            }
            if(arr[mid]>key)
            {
                high=mid-1;
            }
        }
        return -mid-1;
     }