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::prelude::*;

fn main() {
    let stdin = std::io::stdin();
    let mut reader = std::io::BufReader::new(stdin.lock());
    let mut s = String::new();
    reader.read_line(&mut s).unwrap();
    let s = s.trim();
    let abcd: Vec<i32> = s.chars().map(|x| x.to_string().parse().unwrap()).collect();
    let a = abcd[0];
    let b = abcd[1];
    let c = abcd[2];
    let d = abcd[3];

    let abcd = [
        [a, b, c, d],
        [a, -b, c, d],
        [a, b, -c, d],
        [a, b, c, -d],
        [a, -b, -c, d],
        [a, b, -c, -d],
        [a, -b, c, -d],
        [a, -b, -c, -d],
    ];
    let ans = abcd
        .iter()
        .filter(|x| x.iter().sum::<i32>() == 7)
        .nth(0)
        .unwrap();
    println!("{}{:+}{:+}{:+}=7", ans[0], ans[1], ans[2], ans[3]);
}