```One cow from each of N farms (1 <= N <= 1000) conveniently numbered
1..N is going to attend the big cow party to be held at farm #X (1
<= X <= N). A total of M (1 <= M <= 100,000) unidirectional (one-way)
roads connects pairs of farms; road i requires Ti (1 <= Ti <= 100)
units of time to traverse.

Each cow must walk to the party and, when the party is over, return
to her farm. Each cow is lazy and thus picks an optimal route with
the shortest time. A cow's return route might be different from her
original route to the party since roads are one-way.

Of all the cows, what is the longest amount of time a cow must spend
walking to the party and back?

INPUT FORMAT:

* Line 1: Three space-separated integers, respectively: N, M, and X

* Lines 2..M+1: Line i+1 describes road i with three space-separated
integers: Ai, Bi, and Ti. The described road runs from farm Ai
to farm Bi, requiring Ti time units to traverse.

SAMPLE INPUT :

4 8 2
1 2 4
1 3 2
1 4 7
2 1 1
2 3 5
3 1 2
3 4 4
4 2 3

INPUT DETAILS:

Four cows; eight roads; party at farm 2.

OUTPUT FORMAT:

* Line 1: One integer: the maximum of time any one cow must walk.

SAMPLE OUTPUT :

10

OUTPUT DETAILS:

Cow 4 proceeds directly to the party (3 units) and returns via farms 1 and
3 (7 units), for a total of 10 time units.

```