import math


def get_sqrt(large_num):
    sq = 0
    while (sq * sq) <= large_num:
        if (sq * sq) == large_num:
            return sq, True
        sq += 1
    return math.sqrt(large_num), False


[r, x1, y1, x2, y2] = map(int, raw_input('').split(' '))
distance, is_integer = get_sqrt(pow(y2 - y1, 2) + pow(x2 - x1, 2))
if is_integer and (distance % (2 * r)) == 0:
    print distance / (2 * r)
else:
    print (int(distance / (2 * r)) + 1)
