River Crossing       river.X

Farmer John is herding his N cows (1 <= N <= 2,500) across the
expanses of his farm when he finds himself blocked by a river.
A single raft is available for transportation.

FJ knows that he must ride on the raft for all crossings and that
that adding cows to the raft makes it traverse the river more slowly.

When FJ is on the raft alone, it can cross the river in M minutes
(1 <= M <= 1000).  When the i cows are added, it takes M_i minutes
(1 <= M_i <= 1000) longer to cross the river than with i-1 cows
(i.e., total M+M_1 minutes with one cow, M+M_1+M_2 with two, etc.).
Determine the minimum time it takes for Farmer John to get all of
the cows across the river (including time returning to get more
cows).

PROBLEM NAME: river

INPUT FORMAT:

* Line 1: Two space-separated integers: N and M

* Lines 2..N+1: Line i+1 contains a single integer: M_i

SAMPLE INPUT:

5 10
3
4
6
100
1

INPUT DETAILS:

There are five cows. Farmer John takes 10 minutes to cross the river
alone, 13 with one cow, 17 with two cows, 23 with three, 123 with
four, and 124 with all five.

OUTPUT FORMAT:

* Line 1: The minimum time it takes for Farmer John to get all of the
        cows across the river.

SAMPLE OUTPUT:

50

OUTPUT DETAILS:

Farmer John can first cross with three cows (23 minutes), then
return (10 minutes), and then cross with the last two (17 minutes).
23+10+17 = 50 minutes total.