n = int(input())
tot_a = 0
tot_b = 0
ans = 0
AB = [list(map(int, input().split())) for _ in range(n)]
for a, b in AB[::-1]:
    bef = b * tot_a
    aft = a * tot_b
    ans += max(bef, aft)
    tot_a += a
    tot_b += b

print(ans)