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(Martingale: Starting with a unit-for-one bet in a casino, you choose to double your bet after each loss until you make a profit and return to unit-one in the next bet. This method has a strong temptation. Many people choose it because they can make up for all the losses and make good profits once they win. But at the same time, there are certain risks. When the basic bet increases gradually, if the principal is not enough to meet the amount of capital that should be put in, there will be the possibility of no return.)