import math
r, x , y ,x1,y1= input().split()
steps =0
x= int(x)
x1 = int(x1)
y = int(y)
y1= int(y1)
r = int(r)
d =math.sqrt((x-x1)**2 + (y-y1)**2)
while (2*r < (d)):
    steps = steps +1
    d =d - 2*r
if (d!= 0):
    print(steps+ 1)
else :
    print ('0')