
from math import ceil, inf, sqrt
import sys

def pro(x,y,p,q,r):
    if((x,y)==(p,q)):
        print(0)
        return
    dist=(x-p)**2 + (y-q)**2
    dist=sqrt(dist)
    # each step cirle moves by 2r ---r**2

    ans= ceil( dist/(2*r))
    print(ans)


t=1
for i in range(t):
    r,x,y,p,q=list(map(int,input().split()))
    
    pro(x,y,p,q,r)