Highest high in the last 500 bars

I want to put an arrow on top of the bar that has the highest high in the last 500 bars. only one bar should be marked. The below code returns many bars.

Code:

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PlotShapes( shapeDownTriangle*IIf(HHVBars(High,500)==0, 1, 0 ), colorGreen, 0, H, -30 );

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Highest high in the last 500 bars