from sys import stdin

r, x1, y1, x2, y2 = map(int, stdin.readline().rstrip().split(" "))
r = 2*r

distance = ((x2-x1)**2 + (y2-y1)**2)**0.5

res = distance//r
if distance%r:
    print(int(res+1))
else:
    print(int(res))