There is no 100% purchase right, only 3 times the investment method can make money
For example, if you lose 10 rupees the first time, you will buy 30 rupees next time.
For example, if you lose 30 rupees the second time, you will buy 90 rupees next time.
For example, if you lose 90 rupees for the third time, you will buy 270 rupees next time.
For example, if you lose 270 rupees for the fourth time, you will buy 810 rupees next time.
Buy 810 ---If you win, you can earn 810-270-90-30-10 = 410rs
