CF913C Party Lemonade

A New Year party is not a New Year party without lemonade! As usual, you are expecting a lot of guests, and buying lemonade has already become a pleasant necessity. Your favorite store sells lemonade in bottles of $ n $ different volumes at different costs. A single bottle of type $ i $ has volume $ 2^{i-1} $ liters and costs $ c_{i} $ roubles. The number of bottles of each type in the store can be considered infinite. You want to buy at least $ L $ liters of lemonade. How many roubles do you have to spend?

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In the first example you should buy one 8-liter bottle for 90 roubles and two 2-liter bottles for 30 roubles each. In total you'll get 12 liters of lemonade for just 150 roubles. In the second example, even though you need only 3 liters, it's cheaper to buy a single 8-liter bottle for 10 roubles. In the third example it's best to buy three 1-liter bottles for 10 roubles each, getting three liters for 30 roubles.