An array lists a company's income and expenses in order. What is the fewest expenses you must move to the end so that the running balance never goes negative?

An array records a company's income (positive) and expenses (negative) over time, and the running balance may never be negative. You may move expenses to the end of the year. What is the fewest expenses you must move? The total of the array is at least 0 and n is at most 100,000.