Script help

[Rakez68]

I really had hard time trying to figure out how to solve it, but it just doesn't pop to my head. Why does it whine about the line (16, 24) which is
(int i=1;i<=4;i++)

No, I don't know what to do. It's a shame because I really want to learn these things

for(int i=1;i<=4;i++) AddUseItemCallback("", "Chem"+i, "GetAcidComplete", "UsedChemsOnPot", true, 0);
I first had only 3 strings,but if the wiki said there was supposed to be 4 strings, i added 1. now atleast the amount of strings match.

But it still doesn't work.