from math import *
r , x , y , x1 , y1 = [int(x) for x in raw_input().split()]

d = sqrt(float((x - x1) * (x - x1) + (y- y1) * (y - y1)))

ans = 0

if d > 0:
    r = 2 * float(r)
    ans = d / r
    x = d - float(int(ans)) * r
    if x == 0.0:
        ans = int(ans)
    else:
        ans = int(ans) + 1
        
print ans


