import random
from sys import stdin
input = stdin.readline

def gcd(a, b):
    if a == 0:
        return b
    return gcd(b % a, a)


def lcm(a, b):
    return (a * b) / gcd(a, b)

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