


def func(r,x1,y1,x2,y2):
    x = x2 - x1
    y = y2 - y1
    dist = (x*x + y*y)**(1/2)
    i = 0
    while dist > 0:
        dist = dist - 2*r
        i = i+1
    return i
        
a = list(map(int,input().split()))

print(func(a[0] , a[1], a[2], a[3], a[4])) 

