P is the golden section point of segment Mn, MP is greater than Mn, and MP = (root 5-1), then what is Mn equal to?

P is the golden section point of segment Mn, MP is greater than Mn, and MP = (root 5-1), then what is Mn equal to?

MP/MN=(√5-1)/2
MP=√5-1
So Mn = 2