What is the minimum waiting period (iddah) for a divorced woman whose waiting period is three menstrual cycles, such that if her husband were to take her back, she could not claim that the waiting period had ended after three menstruations?

The Maliki school of thought holds that the shortest possible duration for three menstrual periods to occur is one month. This is conceivable if menstruation begins and ends before dawn, followed by a fifteen-day period of purity, then another menstruation that begins and ends before dawn, and finally, a third menstruation that starts at sunset on the last day of the month. As for the Hanbalis, they are of the opinion that the shortest period for the 'iddah (waiting period) to conclude by quru’ (menstruations) is twenty-nine days and two moments. If the quru’ are periods of purity, then the shortest is twenty-eight days and two moments. As for the Shafi'i and Hanafi schools, they hold that the minimum duration for the 'iddah must be longer than what has been mentioned, because the shortest period of purity between two menstruations is no less than fifteen days. The minimum duration for menstruation is one full day according to the Shafi'is, and three days according to the Hanafis.