from math import ceil
 
def INPUT():
    return [int(x) for x in input().split(' ')]
 
def main():
    r, x1, y1, x2, y2 = INPUT()
 
    dis =  ((x1 - x2)**2 +(y1 - y2)**2) ** 0.5
 
    ans = ceil(dis/(2 * r))
 
    print(ans)
 
if __name__=="__main__":
    main()

