Total RAM across telegraf nodes

I’m trying to add a simple graph that would sum every point in time for all telegraf mem fields, so e.g. with two nodes: 240MB and 320MB, it would show: 560MB.

The separate nodes are set to mean() and seem to show the correct values.

I have tried to stack it, mean(), sum(), median(), … nothing can simply add the X nodes together, what’s the right query?