Problem:
Score : 300 points

Problem Statement

Sitting in a station waiting room, Joisino is gazing at her train ticket.

The ticket is numbered with four digits A, B, C and D in this order, each between 0 and 9 (inclusive).

In the formula A op1 B op2 C op3 D = 7, replace each of the symbols op1, op2 and op3 with + or - so that the formula holds.

The given input guarantees that there is a solution. If there are multiple solutions, any of them will be accepted.

Constraints

0≤A,B,C,D≤9

All input values are integers.

It is guaranteed that there is a solution.

Input

Input is given from Standard Input in the following format:

ABCD

Output

Print the formula you made, including the part =7.

Use the signs + and -.

Do not print a space between a digit and a sign.

Sample Input 1

1222

Sample Output 1

1+2+2+2=7

This is the only valid solution.

Sample Input 2

0290

Sample Output 2

0-2+9+0=7

0 - 2 + 9 - 0 = 7 is also a valid solution.

Sample Input 3

3242

Sample Output 3

3+2+4-2=7

Solution in Kotlin (1.0.0) (judge verdict: Accepted)

import java.io.PrintWriter
import java.util.*
import java.math.*

val pw = PrintWriter(System.out)


val end: Int = 4
fun dfs(i: Int, num: Int, x: List<Int>, formula: String): String {
    if(i == end) {
        if(num == 7) return formula + "=7"
        else return ""
    } else {
        val cx = x[i]
        val ansPlus = dfs(i+1, num+cx, x, formula+"+$cx")
        val ansMinus = dfs(i+1, num-cx, x, formula+"-$cx")
        return if(ansMinus.isEmpty()) ansPlus else ansMinus
    }
}

fun main(args: Array<String>) {
    val x = read()
    val xInt = x.map { it.toString().toInt() }

    println(dfs(1, xInt[0], xInt, "${xInt[0]}"))
    pw.flush()
}

fun inputList() = 
    readLine()!!.split(" ").map(String::toInt)

fun sum_digits(num_: Long): Long {
    var num = num_
    var rtn: Long = 0
    while(num != 0.toLong()) {
        val tmp = num % 10
        rtn += tmp
        num /= 10
    }
    return rtn
}

/****** Decrared Functions ******/

// IO
fun read() = readLine()!!
fun readInt() = read().toInt()
fun readLong() = read().toLong()
fun readDouble() = read().toDouble()
fun readListOfString() = read().split(" ")
fun readListOfInt() = readListOfString().map { it.toInt() }
fun readListOfLong() = readListOfString().map { it.toLong() }
fun readListOfDouble() = readListOfString().map { it.toDouble() }


fun println(value : Any) {
    pw.println(value)
}

fun gcd(a: Long, b: Long): Long = 
    if(b != 0L) a else gcd(b, a % b)

fun lcm(a: Long, b: Long) = 
    if(b==0L) a else gcd(b, a % b)