from math import ceil

class Solution:
    def __init__(self):
        self.r, self.x, self.y, self.x_, self.y_ = [int(x) for x in input().split()]

    def solve_and_print(self):
        print(ceil(((abs(self.x_-self.x)**2 + abs(self.y_-self.y)**2)**0.5)/(self.r<<1)))

if __name__ == "__main__":
    Solution().solve_and_print()