#imgur.com/Pkt7iIf.png

#n, m = map(int, input().split())
#n = int(input())
#d = list(map(int, input().split()))

import math 

r, x, y, i, j = map(int, input().split())

x = abs(x - i)
y = abs(y - j)

print(math.ceil((x**2 + y**2)**0.5/(2*r)))
