import math

def Amr(r, x1,y1,x2,y2):
    val1=abs(x1-x2)
    val2=abs(y1-y2)
    dis=math.sqrt((val1**2)+(val2**2))
    if val1==0 or val2==0:
        res=int(dis/(r*2))
    else:
        res=int(dis/r)
    return res


aux1, aux2, aux3, aux4, aux5 = input().split(' ')
r = int(aux1)
x1 = int(aux2)
y1 = int(aux3)
x2 = int(aux4)
y2 = int(aux5)

print(Amr(r, x1, y1, x2, y2))