import math
r,x,y,a,b=raw_input().split()
r=int(r)
x=int(x)
y=int(y)
a=int(a)
b=int(b)
def dist(x,y,a,b):
    g=(a-x)*(a-x)
    h=(b-y)*(b-y)
    return math.sqrt(g+h)
print int(dist(x,y,a,b)/(r*math.sqrt(2))+.000001)
