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 Rust (1.15.1) (judge verdict: Accepted)

use std::io::*;
use std::str::FromStr;
use std::collections::HashMap;
use std::collections::BTreeSet;
use std::cmp;
use std::num::Wrapping; // overflowを回避
use std::f64::consts;


fn main() {
    let s: String = read();
    let b = Bit::new(s);
    b.exec();
}


// Bit全探索
struct Bit {
    num: String,
}

impl Bit {
    fn new(num: String) -> Bit {
        Bit {
            num: num,
        }
    }

    fn exec(&self) {
        let vec: Vec<char> = self.num.chars().collect();
        let intNum = self.num.parse::<i64>().unwrap();
        let mut sum: i64 = 0;


        for bit in 0..(1 << (vec.len()-1)) {
            let mut str: String = String::from("");

            for i in 0..vec.len() {
                if (1&bit>>i) == 1 {
                    str = format!("{}{}+", str, vec[i as usize]);
                } else if i == vec.len()-1{
                    str = format!("{}{}", str, vec[i as usize]);
                } else {
                    str = format!("{}{}-", str, vec[i as usize]);
                }
            }

            let mut each_sum: i32 = 0;
            let mut op = '*';
            for c in str.chars() {
                if c == '-' {
                    op = '-';
                } else if c == '+' {
                    op = '+';
                } else {
                    match op {
                        '-' => each_sum -= c.to_string().parse::<i32>().unwrap(),
                        '+' => each_sum += c.to_string().parse::<i32>().unwrap(),
                        '*' => each_sum = c.to_string().parse::<i32>().unwrap(),
                        _ => each_sum = each_sum
                    }
                }
            }

            if each_sum == 7 {
                println!("{}=7", str);
                return;
            }
        }
    }
}

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}