# 507B
from math import ceil,sqrt
t =  input().split()
t = list(map(int, t))
r = t[0]
x = t[1]
y = t[2]
a = t[3]
b = t[4]
d = sqrt((x-a)**2+(y-b)**2)
if d == 0:
    res = 0
else: 
    if r>d:
        res = 1
    else:
        res = ceil(d/(2*r))
print(res)