r,x,y,x1,y1=map(int,input().split())
d=2*r
if x==x1 and y==y1:
    print(0)
else:
    a=(x-x1)*(x-x1)+(y-y1)*(y-y1)
    a=a**0.5
    if a==int(a):
        if int(a)%d==0:
            print(int(a//d))
        else:
            print(int(a//d)+1)
    else:
        print(int(a//d)+1)
