from collections import defaultdict, deque, Counter, OrderedDict
# import threading,sys
import math


def main():
    r, a, b, x, y = [int(i) for i in input().split()]
    dist = (float(x - a)**2 + float(y - b)**2) ** 0.5
    ans = math.ceil(dist / (2 * r))
    print(ans)


if __name__ == "__main__":
    """sys.setrecursionlimit(400000)
    threading.stack_size(40960000)
    thread = threading.Thread(target=main)
    thread.start()"""
    main()
