from sys import stdin, stdout
from math import ceil, sqrt


def distance(x1, y1, x2, y2):
    return sqrt((x1 - x2)**2 + (y1 - y2)**2)


def solve(r, x1, y1, x2, y2):
    dist = distance(x1, y1, x2, y2)
    return int(ceil(dist/(2*r)))


if __name__ == "__main__":
    r, x1, y1, x2, y2 = list(map(int, stdin.readline().rstrip().split()))
    stdout.write(str(solve(r, x1, y1, x2, y2)))

