import math
def minSteps(r,x,y,newX,newY):
    distance = math.sqrt(pow(x-newX,2)+pow(y-newY,2))
    return math.ceil((distance)/(2*r))

r,x,y,newX,newY = [int(x) for x in input().split()] 
print(minSteps(r,x,y,newX,newY))