import math


def dist_2d(x1, y1, x2, y2):
    """
    calculates euclidian distance between two points
    :param x1: point 1 x
    :param y1: point 1 y
    :param x2: point 2 x
    :param y2: point 2 y
    :return: scalar distance
    """
    dist = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)
    return dist