laba 18(b) Calc for pi

eps = inputbox("Введите точность:","Окно ввода. Попов  Игорь")
eps = eps * 1
pi = 3.1415926535897932384626433832795
t1 = Time
n = 1

private function q(n,tochnost)
a = 1 / (n*n)
q = 1
do while abs(a) > tochnost
n = n + 1
a = 1 / (n*n)
q = q + a
loop
end function

r_pi=sqr(q(n,eps)/(1/6))

t2 = Time
dt=FormatDateTime(t2-t1)

msgbox "Eps=" & eps & vblf & _
       "Ист. Pi=" & pi & vblf & _
       "Расч. Pi=" & r_pi & vbLf & _
       "n=" & n & vblf & _
       "dt=" & dt _
       ,vbok,"Попов Игорь"