r,x,y,x1,y1=map(int,input().split(' '))
dist=pow(((x-x1)*(x-x1)+(y-y1)*(y-y1)),0.5)
if(dist==0.0):
    print(0)
else:
    z=(dist/(2*r))
    if((z-int(z)==0.0)):
       print(int(z))
    else:
       print(int(z+1)) 
