from sys import stdin,stdout
from math import gcd, sqrt, ceil
ii1 = lambda: int(stdin.readline().strip())
is1 = lambda: stdin.readline().strip()
iia = lambda: list(map(int, stdin.readline().strip().split()))
isa = lambda: stdin.readline().strip().split()
mod = 1000000007

r, x, y, x1, y1 = iia()
d = sqrt(pow(x1 - x, 2) + pow(y1 - y, 2))
ans = ceil(d/(2*r))
print(ans)