listl = []
listr = []
with open("input") as lines:
    for line in lines.readlines():
        line = line.rstrip()
        print(line)
        spli = line.split(" ")
        listl.append(int(spli[0]))
        listr.append(int(spli[-1]))

assert len(listl) == len(listr)

listl.sort()
listr.sort()

dtot = 0

for i in range(len(listl)):
    l = listl[i]
    d = listr.count(l) * l
    dtot += d
    print(l, d)

print(dtot)