import math
r, x, y, x1,y1 = map(int, input().split())
r =r *2

k = math.sqrt(((x1 -x) *(x1 -x)) + ((y1 -y) *(y1 -y)))  

if(k == k//1 and (k//1) % r ==0):
    print(int(k//r))
else:
    print(int(k//r +1))  