Relative Strength Index with third band

study(title="Relative Strength Index with third band", shorttitle="RSI 3band")
src = close, len = input(14, minval=1, title="Length")
band2pos = input(50.0, type=float, title="third rsi band", minval=1, maxval=100)
up = rma(max(change(src), 0), len)
down = rma(-min(change(src), 0), len)
rsi = down == 0 ? 100 : up == 0 ? 0 : 100 - (100 / (1 + up / down))
plot(rsi, color=purple)
band1 = hline(70)
band0 = hline(30)
band2 = hline(band2pos)
fill(band1, band0, color=purple, transp=90)