how do you add two numbers from messages?

    May 03 2014 | 6:53 pm
    let's say I send a 5 then I send a 10 (via messages)
    I need an object to remember 5, then add 10, result of 15.
    in other words, I need to send a series of numbers to an object and have it add the numbers every time.
    any object for this?
    just tried accum. I was able to accomplish this by sending a 0 to the first inlet to clear the value after I'm done adding numbers. This works.