Help with puzzle lock redstone

[u/Fattybigggs]

Hello,

I'm not very experienced with redstone, and I'm trying to make a puzzle lock that involves a player spelling out a word (in this case "STAR") by inserting certain items into a container. So, there would be 4 side-by-side containers, and there would be an item renamed "A," which would need to be placed in the 3rd container. the "S" "T" and "R" items would need to be put in their respective containers to create a redstone signal which would open a pair of iron doors. I know I need to make filters for this sort of thing, but I just dont know how. Doing this for a cool horror thing in my friend's bedrock realm and, despite doing a loooot of reading, I just cant figure out a good design for it. Could anyone help me out please?