import sys
from math import sqrt

def distance(a, b, c, d):
    dx = (a-c)
    dy = (b-d)
    return sqrt(dx*dx + dy*dy)

r, sx, sy, dx, dy = (int(x) for x in sys.stdin.readline().split())
d = distance(sx, sy, dx, dy)
diam = 2*r
answer = 0
while d > r:
    #print(d)
    d -= diam
    answer += 1
if d != 0:
    answer += 1
print(answer)
