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 Ruby (2.3.3) (judge verdict: Accepted)

class Solution
    def initialize(target, inputs)
        @target = target
        @inputs = inputs
    end

    def dfs(depth, value, form)
        if depth == @inputs.count
            if value == @target
                return true, form + '=' + @target.to_s
            else
                return false, form
            end
        end

        result1, form1 = dfs depth + 1, value + @inputs[depth],
            (depth > 0 ? form + '+' : '') + @inputs[depth].to_s
        if result1 == true
            return result1, form1
        end

        result2, form2 = dfs depth + 1, value - @inputs[depth],
            (depth > 0 ? form + '-' : '') + @inputs[depth].to_s
        if result2 == true
            return result2, form2
        end

        return false, ''
    end

    def solve
        result, form = dfs 0, 0, ''
        if result == true
            return form
        else
            return 'No solution'
        end
    end
end

def main
    #inputs = '1222'.split('').map(&:to_i)
    inputs = STDIN.gets.chomp.split('').map(&:to_i)
    solution = Solution.new(7, inputs)
    puts solution.solve
end

main