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Contest: Task: Related: TaskD TaskF

Score : $500$ points

Problem Statement

There is a directed graph with $N$ vertices numbered $1$ to $N$ and $M$ edges. The $i$-th edge is directed from Vertex $A_i$ to Vertex $B_i$, and there are $C_i$ coins placed along that edge. Additionally, there is a button on Vertex $N$.

We will play a game on this graph. You start the game on Vertex $1$ with zero coins, and head for Vertex $N$ by traversing the edges while collecting coins. It takes one minute to traverse an edge, and you can collect the coins placed along the edge each time you traverse it. As usual in games, even if you traverse an edge once and collect the coins, the same number of coins will reappear next time you traverse that edge, which you can collect again.

When you reach Vertex $N$, you can end the game by pressing the button. (You can also choose to leave Vertex $N$ without pressing the button and continue traveling.) However, when you end the game, you will be asked to pay $T \times P$ coins, where $T$ is the number of minutes elapsed since the start of the game. If you have less than $T \times P$ coins, you will have to pay all of your coins instead.

Your score will be the number of coins you have after this payment. Determine if there exists a maximum value of the score that can be obtained. If the answer is yes, find that maximum value.

Constraints

  • $2 \leq N \leq 2500$
  • $1 \leq M \leq 5000$
  • $1 \leq A_i, B_i \leq N$
  • $1 \leq C_i \leq 10^5$
  • $0 \leq P \leq 10^5$
  • All values in input are integers.
  • Vertex $N$ can be reached from Vertex $1$.

Input

Input is given from Standard Input in the following format:

$N$ $M$ $P$
$A_1$ $B_1$ $C_1$
$:$
$A_M$ $B_M$ $C_M$

Output

If there exists a maximum value of the score that can be obtained, print that maximum value; otherwise, print -1.

Sample Input 1

3 3 10
1 2 20
2 3 30
1 3 45

Sample Output 1

35

Figure of the graph given in Sample Input 1

There are two ways to travel from Vertex $1$ to Vertex $3$:

  • Vertex $1 \rightarrow 2 \rightarrow 3$: You collect $20 + 30 = 50$ coins on the way. After two minutes from the start of the game, you press the button, pay $2 \times 10 = 20$ coins, and you have $50 - 20 = 30$ coins left.
  • Vertex $1 \rightarrow 2$: You collect $45$ coins on the way. After one minute from the start of the game, you press the button, pay $1 \times 10 = 10$ coins, and you have $45 - 10 = 35$ coins left.

Thus, the maximum score that can be obtained is $35$.

Sample Input 2

2 2 10
1 2 100
2 2 100

Sample Output 2

-1

Figure of the graph given in Sample Input 2

The edge extending from Vertex $1$ takes you to Vertex $2$. If you then traverse the edge extending from Vertex $2$ to itself $t$ times and press the button, your score will be $90 + 90t$. Thus, you can infinitely increase your score, which means there is no maximum value of the score that can be obtained.

Sample Input 3

4 5 10
1 2 1
1 4 1
3 4 1
2 2 100
3 3 100

Sample Output 3

0

Figure of the graph given in Sample Input 3

There is no way to travel from Vertex $1$ to Vertex $4$ other than traversing the edge leading from Vertex $1$ to Vertex $4$ directly. You will pick up one coin along this edge, but after being asked to paying $10$ coins, your score will be $0$.

Note that you can collect an infinite number of coins if you traverse the edge leading from Vertex $1$ to Vertex $2$, but this is pointless since you can no longer reach Vertex $4$ and end the game.