I made the point earlier that you can either use multiplication or addition for handling the stride. Watch this:

```
stride = 3
print("Using multiplication")
for h in range(4):
vert_start = h * stride
print(f"h {h}, vert_start {vert_start}")
print("Using addition")
vert_start = 0
for h in range(4):
print(f"h {h}, vert_start {vert_start}")
vert_start = vert_start + stride
```

Running that gives these results:

```
Using multiplication
h 0, vert_start 0
h 1, vert_start 3
h 2, vert_start 6
h 3, vert_start 9
Using addition
h 0, vert_start 0
h 1, vert_start 3
h 2, vert_start 6
h 3, vert_start 9
```

So either method works, but I think the multiplication method is simpler to write and clearer code.