import math
inp = list(map(int,raw_input().split()))
inp1 = list(inp)
raduis = inp1[0]
x = inp1[1]
y = inp1[2]
xd = inp1[3]
yd = inp1[4]
distance = (x - xd)*(x - xd)*1.0 + (y - yd)*(y - yd)*1.0
root = math.sqrt(distance) * 1.0
out = math.ceil(root / (2*raduis))
print int(out)

