import math

def ia():
    line = raw_input()
    line = line.split()
    return map(int, line)

r, x0, y0, x1, y1 = ia()

d = 2*r
R2 = (x0 - x1)**2 + (y0 - y1)**2

print int(math.ceil(math.sqrt(R2)/d))
