s = lambda:map(int,raw_input().split())
r,x,y,xf,yf = s()
dist = (xf-x)**2 +(yf-y)**2
ans = dist**(0.5)
num = (ans-r)//r
if(ans<r):
	print '1'
elif(x == xf and y == yf):
	print '0'
else:
	print int(num)
