```Description

Farmer John went to cut some wood and left N (2 ¡Ü N ¡Ü 100,000) cows eating the grass, as usual.
When he returned, he found to his horror that the cluster of cows was in his garden eating his
beautiful flowers. Wanting to minimize the subsequent damage, FJ decided to take immediate action
and transport each cow back to its own barn.

Each cow i is at a location that is Ti minutes (1 ¡Ü Ti ¡Ü 2,000,000) away from its own barn.
Furthermore, while waiting for transport, she destroys Di (1 ¡Ü Di ¡Ü 100) flowers per minute.
No matter how hard he tries, FJ can only transport one cow at a time back to her barn. Moving
cow i to its barn requires 2 ¡Á Ti minutes (Ti to get there and Ti to return). FJ starts at the
flower patch, transports the cow to its barn, and then walks back to the flowers, taking no
extra time to get to the next cow that needs transport.

Write a program to determine the order in which FJ should pick up the cows so that the total
number of flowers destroyed is minimized.

Input

The input consists of several test cases. For each test case:
Line 1: A single integer N
Lines 2..N+1: Each line contains two space-separated integers, Ti and Di, that describe a single
cow's characteristics

Output

Line 1: A single integer that is the minimum number of destroyed flowers

Sample Input

6
3 1
2 5
2 3
3 2
4 1
1 6

Sample Output

86

Hint

FJ returns the cows in the following order: 6, 2, 3, 4, 1, 5. While he is transporting cow 6 to the
barn, the others destroy 24 flowers; next he will take cow 2, losing 28 more of his beautiful flora.
For the cows 3, 4, 1 he loses 16, 12, and 6 flowers respectively. When he picks cow 5 there are no
more cows damaging the flowers, so the loss for that cow is zero. The total flowers lost this way
is 24 + 28 + 16 + 12 + 6 = 86.

Source

USACO 2007 January Silver
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