import sys
import math
input = sys.stdin.readline

r, x, y, x1, y1 = map(int, input().split())

dis = math.sqrt((x - x1)**2 + (y - y1)**2)
ans = math.floor(dis / (r * 2))
rem = dis % (r * 2)
if rem > 0:
    ans += 1
print(ans)