from sys import stdin, setrecursionlimit
from collections import deque
import math 
input = stdin.readline
setrecursionlimit(int(2e5))
def getstr(): return input()[:-1]
def getint(): return int(input())
def getints(): return list(map(int, input().split()))
def getint1(): return list(map(lambda x : int(x) - 1, input().split()))
jn = lambda x,l: x.join(map(str,l))
 
MOD = 10 ** 9 + 7
y, n = "YES", "NO"
# inputs=open('input.txt','r')
 
# n=inputs.readlines()
 
def solve():
    r,x1,y1,x2,y2 = getints()
    d = 2*r
    dis =  math.sqrt((x1 -x2)*(x1 - x2) +
         (y1 - y2)*(y1 - y2)) 
    print(-int(-dis//(d)))
 
 
if __name__ == "__main__":
    # solve()
    # for t in range(getint()):
    #     print("Case #{}: ".format(t + 1), end="")
    #     solve()
    #for _ in range(int(inputs.readline())):
    solve()