import math
def dist(x1,y1,x2,y2):
    a = (x1-x2)**2
    b = (y1-y2)**2
    c = math.sqrt(a+b)
    return(c)

r,x,y,x2,y2 = map(int,input().split())
distance = dist(x,y,x2,y2)
print(math.ceil(distance/(2*r)))