Unbounded Knapsack - Problem Statement

You have $n$ item types. Each type $i$ has weight $w_i$ and value $v_i$. You can take each type any number of times (including zero).

Your bag holds at most $W$ total weight. Find the maximum value. Example: Items are ($weight=2$, $value=3$) and ($weight=3$, $value=4$). Capacity $W = 7$. Take three of item 1: weight $6$, value $9$. But two of item 1 and one of item 2 gives weight $2+2+3=7$, value $3+3+4=10$. Best is $10$.