Count P&L windows summing to k

You are given a list of daily P&L values (integers, possibly negative) and a target $k$. Count the contiguous stretches of days whose total P&L is exactly $k$. For example, with P&L $[1, 2, -1, 1, 2, -3, 3]$ and $k = 3$ the answer is 5. Aim for $O(n)$ time.