import math

def solve(r, x0, y0, x1, y1):
    d = math.sqrt((x0-x1) ** 2 + (y0-y1) ** 2)

    return math.ceil(d/(2*r))



r, x0,y0,x1,y1 = list(map(int, input().split(" ")))

print(solve(r, x0, y0, x1,y1))
