Problem:
Score : 100 points

Problem Statement

Joisino wants to evaluate the formula "A op B".
Here, A and B are integers, and the binary operator op is either + or -.
Your task is to evaluate the formula instead of her.

Constraints

1≦A,B≦10^9

op is either + or -.

Input

The input is given from Standard Input in the following format:

A op B

Output

Evaluate the formula and print the result.

Sample Input 1

1 + 2

Sample Output 1

3

Since 1 + 2 = 3, the output should be 3.

Sample Input 2

5 - 7

Sample Output 2

-2

Solution in Kotlin (1.0.0) (judge verdict: Runtime Error)

import java.util.*

val mod: Long = (Math.pow(10.0, 9.0) + 7).toLong()

fun main(args: Array<String>) {
    val sc = Scanner(System.`in`)
    val n = sc.nextInt()
    val aList = mutableListOf<Int>()
    for (i in 0 until n) {
        aList.add(sc.nextInt())
    }

    var bList = mutableListOf<Int>()
    for (i in 1..n / 2) {
        bList.add(n - i * 2 + 1)
    }
    val reversed = bList.reversed().toMutableList()
    if (n % 2 != 0) {
        reversed.add(0, 0)
    }
    bList = (bList + reversed).toMutableList()

    if (aList.sorted() != bList.sorted()) {
        println(0)
        return
    }

    val ans = Math.pow(2.0, (n / 2).toDouble()) % mod
    println(ans.toLong())
}