import math
r, x, y, x2, y2= (int(x) for x in input().split())

razdalja = math.sqrt((x2 - x)**2 + (y2 - y)**2)


if razdalja % (2 * r) != 0:
    print(int(razdalja // (2 * r)) + 1)


else:
    print(int(razdalja / (2 * r)))