import math


def dist(x, xx, y, yy):
    fix = (x - xx) ** 2 + (y - yy) ** 2
    fix = math.sqrt(fix)
    return fix


r, x, y, xx, yy = map(int, input().split())
ans = math.ceil(dist(x, xx, y, yy) / (2 * r))
print(ans)
