#!/usr/bin/env python3
from math import ceil


def main():
    r, x, y, x_g, y_g = list(map(int, input().split()))
    distance = ((x - x_g) ** 2 + (y - y_g) ** 2) ** 0.5
    print(ceil(distance / (2 * r)))


if __name__ == '__main__':
    main()
