In a bombing attack, there is 50% chance that a bomb will hit the target. At least two independent hits are required to destroy the target…

In a bombing attack, there is $\displaystyle 50$% chance that a bomb will hit the target. At least two independent hits are required to destroy the target completely. Then the minimum number of bombs, that must be dropped to ensure that there is at least $\displaystyle 99$% chance of completely destroying the target, is \_\_\_\_.