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P1001 Fib3 Queue

Difficulty: $\color{grey}100$

Problem Statement

You need to create a Fib3 Queue. (A Fib3 Queue is a queue that from the 4th element on, its value equals the sum of the three consecutive elements before.) We will give you the $x^{\rm th}$, the $(x-1)^{\rm th}$ and the $(x-2)^{\rm th}$ element and you need to work out the 1st element.

Constraints

• $3 \le x \le 100$
  
• $1 \le q_{x-2} \le q_{x-1} \le q_{x} \le 100$

Input

$x$
$q_x\ q_{x-1}\ q_{x-2}$

Note that $q_x$, $q_{x-1}$, $q_{x-2}$ may be not in order.

Output

Output the queue's 1st element.

Samples

Input 1

4
9 5 3

Output 1

1

We can get the answer by calculating $9-5-3=1$.

Input 2

3
3 5 9

Output 2

3

We can get the answer $3$ immediately from the input.

Input 3

10
3 5 8

Output 3

-7

Input 4

100
100 100 100

Output 4

-36198145043300

Note that the result may not fits in a $32$bit integer.