import math
r,x0,y0,x1,y1 = map(float,raw_input().split())
if x0 == x1 and y0 == y1:
    print 0
else:
    dis = math.sqrt((x0-x1)**2 + (y0-y1)**2)
    answer = 0
    while dis > 0:
        dis -= r*2
        answer += 1
    print answer
