l=list(map(int,input().split()))
r=l[0]
x1=l[1]
y1=l[2]
x2=l[3]
y2=l[4]
res=(((x2-x1)**2)+((y2-y1)**2))**0.5
if res!=0 and res%int(res)!=0:
    res=int(res)+1
c=res//(r*2)
if res%(r*2)!=0:
    c+=1
print(int(c))