import math

def ans():
    r, x1, y1, x2, y2= [int(i) for i in input().split()]
    d= math.sqrt(((x2- x1)**2)+((y2- y1)**2))
    #print(d, d/(2*r))
    if d%(2*r)== 0:
        print(int(d/(2*r)))
    else:
        print(int(d/(2*r))+ 1)
        
    return

ans()