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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC079
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] arr = Console.ReadLine()
                .ToCharArray()
                .Select(s => int.Parse(s.ToString()))
                .ToArray();

            int A = arr[0];
            int B = arr[1];
            int C = arr[2];
            int D = arr[3];

            int len = arr.Length;

            for (uint bit = 0; bit < (1 << len - 1); bit++)
            {
                //Console.WriteLine(Convert.ToString(bit, toBase: 2));
                int result = 0;

                char operator1 = (((bit >> len - 2) & 1) == 1) ? '+' : '-';
                char operator2 = (((bit >> len - 3) & 1) == 1) ? '+' : '-';
                char operator3 = (((bit >> len - 4) & 1) == 1) ? '+' : '-';

                calc(ref result, A, '+');
                calc(ref result, B, operator1);
                calc(ref result, C, operator2);
                calc(ref result, D, operator3);

                if (result == 7)
                {
                    Console.WriteLine($"{A}{operator1}{B}{operator2}{C}{operator3}{D}=7");
                    Console.ReadLine();
                }
            }
        }

        static void calc(ref int baseNum, int otherNum, char cOperator)
        {
            if (cOperator == '+')
            {
                baseNum += otherNum;
            }
            else
            {
                baseNum -= otherNum;
            }
        }
    }
}