from fractions import Fraction
urns = [[4,3],[5,4],[4,4]]
red = []
black = []
for lst in urns:
    red.append(Fraction(lst[0],sum(lst)))
    black.append(Fraction(lst[1],sum(lst)))
doub = []
for i in range(len(red)-1):
    for j in range(i+1, len(red)):
        doub.append(red[i]*red[j])
final = []
for j in range(len(black)):
    final.append(doub[j]*black[len(black)-j-1])
print(sum(final))