import math
r,x,y,a,b=map(int,input().split())

d = (a-x)*(a-x) + (b-y)*(b-y)

sd = d


d = pow(d,0.5)



di = int(d)
Q = False


if(di*di == sd):
    Q=True
else:
    di=di+1
    if(di*di==sd):
        Q=True
    else:
        di=di-2
        if(di*di==sd):
            Q=True

if(Q):
    f=0
    if(di%(2*r)!=0):
        f=1
    if(di//(2*r)==0 and f):
        f+=1
    print(di//(2*r)+f)
else:
    di=int(math.floor(d))
    f=1
    if(di//(2*r)==0):
        f+=1
    print(di//(2*r)+f)
