Let $G$ be an additive finite abelian group with exponent $\exp (G) = n$. For a sequence $S$ over $G$, let f$(S)$ denote the number of non-zero group elements which can be expressed as a sum of a nontrivial subsequence of $S$. We show that for every zero-sum free sequence $S$ over $G$ of length $|S| = n+1$ we have f$(S) \ge 3n-1$.