Find the coins required which sum to S Given a list of $N$ coins, their values $V_1, V_2, \cdots , V_N$, and a parameter of a total sum $S$. Find the coins the sum of which is S (we can use each coin at most once).

I was recently studying the very same problem from topcoder.com but there "we can use each coin any number of times". I am just stuck here if we can use each coin only once and not multiple times.

It will be very helpful if you can help or just give a hint. (this is not my homework quiz :P)
Hint: Dynamic programming on this subproblem: "Can I get a sum of $x$ if I can use only the $k$ smallest coins?"