Suppose you want to hedge a stock portfolio using the S&P 500 Index futures. One E-mini S&P 500 Index futures contract covers 50 times the index value. The futures price of the S&P 500 Index is 4,500. The current value of the portfolio is $9 million, and the beta of the portfolio is 0.9. If you want to decrease the portfolio beta to 0.5, you should trade _____ futures contracts