create a maximum raster using gdal_calc

I have an NDVI-Time series (24 tiffs from one year). What I would like to calculate is one single Raster with the Maximum NDVI-value for each pixel from all 24 images. I thought about using gdalcalc but I cannot find the right syntax to calculate the maximum of a my inputfiles:

Example for 2 Layers:

shell("E:/Programme/OSGeo4W.bat; gdal_calc -A E:/IVFL/Somalia/NDVI/201401_001_NDVI_NAfill.tif -B E:/IVFL/Somalia/NDVI/201409_121_NDVI_NAfill.tif --outfile E:/IVFL/Somalia/NDVI_maximum.tif --calc=(max(A,B))")


calc=max(A,B) always gives me an error.

And in the end I even have 24 input files and not only 2. Does anyone know the syntax (numpy) to calculate the maximum?

--calc="maximum(A,B)"

--calc="maximum(maximum(maximum(A,B),maximum(C,D)),maximum(maximum(E,F),maximum(G,H)))"