import math

def main():
    xy = map(int, raw_input().split())
    r = xy[0]
    x = xy[1]
    y = xy[2]
    x_prime = xy[3]
    y_prime = xy[4]

    dist = math.sqrt((x_prime-x)*(x_prime-x)+(y_prime-y)*(y_prime-y))

    print int(math.ceil(dist/(2*r)))

main()
