E - Peddler

Score : $500$ points

Problem Statement

In Takahashi Kingdom, there are $N$ towns, called Town $1$ through Town $N$.
There are also $M$ roads in the kingdom, called Road $1$ through Road $M$. By traversing Road $i$, you can travel from Town $X_i$ to Town $Y_i$, but not vice versa. Here, it is guaranteed that $X_i < Y_i$.
Gold is actively traded in this kingdom. At Town $i$, you can buy or sell $1$ kilogram of gold for $A_i$ yen (the currency of Japan).

Takahashi, a traveling salesman, plans to buy $1$ kilogram of gold at some town, traverse one or more roads, and sell $1$ kilogram of gold at another town.
Find the maximum possible profit (that is, the selling price minus the buying price) in this plan.

Constraints

• $2 \le N \le 2 \times 10^5$
• $1 \le M \le 2 \times 10^5$
• $1 \le A_i \le 10^9$
• $1 \le X_i \lt Y_i \le N$
• $(X_i, Y_i) \neq (X_j, Y_j) (i \neq j)$
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

$N$ $M$

$A_1$ $A_2$ $A_3$ $\dots$ $A_N$

$X_1$ $Y_1$

$X_2$ $Y_2$

$X_3$ $Y_3$

$\hspace{15pt} \vdots$

$X_M$ $Y_M$

Output

Print the answer.

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

3

We can achieve the profit of $3$ yen, as follows:

• At Town $1$, buy one kilogram of gold for $2$ yen.
• Traverse Road $2$ to get to Town $2$.
• Traverse Road $1$ to get to Town $4$.
• At Town $4$, sell one kilogram of gold for $5$ yen.

5 5
13 8 3 15 18
2 4
1 2
4 5
2 3
1 3

10

We can achieve the profit of $10$ yen, as follows:

• At Town $2$, buy one kilogram of gold for $8$ yen.
• Traverse Road $1$ to get to Town $4$.
• Traverse Road $3$ to get to Town $5$.
• At Town $5$, sell one kilogram of gold for $18$ yen.

3 1
1 100 1
2 3

-99

Note that we cannot sell gold at the town where we bought the gold, which means the answer may be negative.