from math import sqrt
yo=list(map(int,input().split()))
r=yo[0]
x=yo[1]
y=yo[2]
xx=yo[3]
yy=yo[4]
dist=sqrt((x-xx)**2+(y-yy)**2)
di=int(dist//(r*2))
#print(dist)
#print(di)
if dist==0:
	print(0)
elif dist<r:
	print(1)
elif dist%(2*r)==0:
	print(di)
else:	
	print((di)+1)