import math
r, x, y, x1, y1 = list(map(int, input().rstrip().split()))
dist = math.sqrt(math.pow(x1 - x, 2) + math.pow(y1 - y, 2))
q = dist // (2 * r)
rem = dist % (2 * r)
count = q
if rem > 0:
    count += 1
print(int(count))