Behavior of an algorithm with inner loop step by 2 and outer loop decrements inner loop times

Question

I designed an algorithm like this but I do not know how to perform its analysis to determine how it runs $($$O(n)$, $O(n^2)$, $O(log(n)$, $etc$$)$

m = some constant
for i = 1 to n
{
    for j = 1 to m step 2
    {
        // do some stuff here
    }
    m = m - 2
}

Can you please provide a clue to solve my issue? This is a homework and I only have to deliver the algorithm, but I want to go farther and determine its behavior. I have analyzed other (maybe simpler) algorithms but this is kind of different of what I have seen.

Respectfully,

Jorge Maldonado