from math import sqrt, ceil


def distance(r, x1, y1, x2, y2):
    return ceil(sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)) / (2 * r))


R, X1, Y1, X2, Y2 = [int(i) for i in input().split()]
print(distance(R, X1, Y1, X2, Y2))
