import math
def distance(x1 , y1 , x2 , y2): 
  
    # Calculating distance 
    return math.sqrt(math.pow(x2 - x1, 2) +
                math.pow(y2 - y1, 2) * 1.0)
                
inp = list(map(int,input().split()))
r,x1,y1,x2,y2 = inp[0],inp[1],inp[2],inp[3],inp[4]

dist = distance(x1,y1,x2,y2)
final = math.ceil(dist/(2*r))
print(final)
