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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <math.h>
#include <string>
#include <sstream>

using namespace std;
istringstream iss;
long long sum, num, c;
string S, S2;

bool cal(string s, int x){
    //cout << s << " " << s.size() << " " << x << endl;
    if(x == s.size()){
        sum = 0;
        iss = istringstream(s.substr(0,1));
        iss >> num;
        //cout << "num = "  << num << endl;
        //cout << x;
        for(int i=1;i<s.size();i++){
            if(s.substr(i,1)=="+"){
                sum += num;
                num = 1;
            }
            else if(s.substr(i,1)=="-"){
                sum += num;
                num = -1;
            }
            else{
                iss = istringstream(s.substr(i,1));
                iss >> c;
                num *= c;
                //if(s == "3141592653")cout << "num = "  << num << "c = "  << c << endl;
            }
            //cout << "num = "  << num << endl;
        }
        //cout << "num = "  << num << endl;
        sum += num;
        //cout << sum << endl;
        if(sum == 7){
            S2 = s;
            //cout << "good" << endl;
            return true;
        }
        else {
            //cout << "bad" << endl;
            return false;
        }
        //cout << "sum=" << sum << endl;
    }
    
    else {
        string s2 = s;
        if(cal(s.insert(x,"+"), x+2)) return true;
        s = s2;
        if(cal(s.insert(x,"-"), x+2)) return true;
        else return false;
    }


}

int main(){
    
    cin >> S;
    if(cal(S, 1)){
        cout << S2 << "=7";
    };
    
    //S.insert(1,"+");
    //cout << S;

    cout << endl;
}