def distance(v_1 , v_2 ) :
    x = ( v_1[0] - v_2[0] ) ** 2
    y = ( v_1[1] - v_2[1] ) ** 2
    dis = ( x + y ) ** ( 1/2 )
    return dis

def no_of_steps(r, c_1, c_2 ) :
    steps = 0
    dis = distance(c_1, c_2 )
    while dis > 0 :
        steps += 1
        dis -= 2 * r
    return steps

if __name__ == "__main__" :
    l = list( map ( int , input().strip().split() ))
    r = l[0]
    c_1 = l[1 : 3]
    c_2 = l[3 : 5]
    print( no_of_steps( r, c_1, c_2 ) )

