def _get_high_res_img_url(img_url):
    """ Returns a modified url pointing to the high resolution version of
    the image
    >>> print(_get_high_res_img_url("https://images-na.ssl-images-amazon.com/\
images/I/513gErH1dML._AC_SX236_SY340_FMwebp_QL65_.jpg"))
    https://images-na.ssl-images-amazon.com/\
images/I/513gErH1dML.jpg
    >>> print(_get_high_res_img_url("https://images-na.ssl-images-amazon.com/\
images/I/51F48HFHq6L._AC_SX118_SY170_QL70_.jpg"))
    https://images-na.ssl-images-amazon.com/\
images/I/51F48HFHq6L.jpg
    """
    high_res_url = img_url.split("._")[0] + ".jpg"
    return high_res_url