import math
def steps(r,x,y,x1,y1):
    distance=math.sqrt((x-x1)**2+(y-y1)**2)
    if distance%(2*r)==0:
        return int(distance//(2*r))
    else:
        return int((distance//(2*r))+1)
l=list(map(int,list(input().split())))
print(steps(l[0],l[1],l[2],l[3],l[4]))