题解 | #搬圆桌#

import math
def s(r,x,y,x1,y1):
    d1 = (x1-x)**2+(y1-y)**2
    d=math.sqrt(d1)
    if d%(2*r)==0:
        s1=d//(2*r)
    else:
        s1=d//(2*r)+1
    return s1
while True:
    try:
        l=list(map(int,input().split()))
        r,x,y,x1,y1=l[:]
        print('%.0f' %s(r,x,y,x1,y1))
    except:
        break