import math

def distancia(x1, y1, x2, y2):
    return math.sqrt((x2-x1)**2+(y2-y1)**2)

def velocitat_port(nomf, eps):

    with open(nomf, 'r') as f:
        cs, cy, v, av=f.readline().strip().split(':')
        for x in f:
            cs2, cy2, v2, av2=x.strip().split(':')
            d=distancia(float(cs), float(cy), float(cs2), float(cy2))
            if d < eps:
                return float(v)
            cs, cy, v, av=cs2, cy2, v2, av2
    return -1.0