Balls are randomly thrown one at a time at a row of 30 open-topped jars numbered 1 to 30. Assuming that each ball lands in some jar, find the smallest number of throws so that there is a better than a...

Balls are randomly thrown one at a time at a row of 30 open-topped jars numbered 1 to 30. Assuming that each ball lands in some jar, find the smallest number of throws so that there is a better than a 60% chance that at least two balls land in the same jar.