import math

def f(d,r):
    k=0
    while (k*2*r<=d-1e-100):
        k+=1
    return k

def main():
    r,x,y,a,b=map(int,raw_input().split())
    d=math.sqrt((x-a)**2+(y-b)**2)
    print f(d,r)

main()
