from math import sqrt, ceil

r, x, y, x1, y1 = map(int, raw_input().split())

distance = sqrt((x-x1)**2 + (y-y1)**2)
steps = 0
if distance <= 2*r:
    steps = 1
if distance == 0.0:
    steps = 0
if distance > 2*r:
    stepCount = distance-distance%(2*r)
    remaining = distance%(2*r)
    steps += stepCount/(2*r)
    #print stepCount
    #print remaining
    if remaining != 0.0:
        steps += 1

print int(steps)            
