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)

// This code is generated by [cargo-atcoder](https://github.com/tanakh/cargo-atcoder)
// Original source code:
/*
use proconio::input;
use itertools::*;

fn apply(op: char, x: i32, y: i32) -> i32 {
    match op {
        '+' => x + y,
        '-' => x - y,
        _ => unreachable!(),
    }
}

fn evaluate(a: &Vec<i32>, ops: &Vec<char>) -> i32 {
    ops.iter().zip(a.iter().skip(1))
        .fold(a[0], |s, (&op, &x)| apply(op, s, x))
}

fn make_expression(a: &Vec<char>, ops: &Vec<char>) -> String {
    a.iter().cloned().interleave(ops.iter().cloned()).chain("=7".chars()).collect()
}

fn operators(n: usize) -> impl Iterator<Item = Vec<char>> {
    (0..n)
        .map(|_| "+-".chars())
        .multi_cartesian_product()
}

fn solve(a: String) -> String {
    let s = a.chars().collect::<Vec<_>>();
    let a = s.iter().map(|c| c.to_digit(10).unwrap() as i32).collect::<Vec<_>>();
    operators(3)
        .filter(|ops| evaluate(&a, &ops) == 7)
        .map(|ops| make_expression(&s, &ops))
        .nth(0)
        .unwrap()
}

fn main() {
    input! {
        a: String,
    }
    let r = solve(a);
    println!("{}", r);
}
*/

fn main() {
    let exe = "/tmp/bin49A21DD1";
    std::io::Write::write_all(&mut std::fs::File::create(exe).unwrap(), &decode(BIN)).unwrap();
    std::fs::set_permissions(exe, std::os::unix::fs::PermissionsExt::from_mode(0o755)).unwrap();
    std::process::exit(std::process::Command::new(exe).status().unwrap().code().unwrap())
}

fn decode(v: &str) -> Vec<u8> {
    let mut ret = vec![];
    let mut buf = 0;
    let mut tbl = vec![64; 256];
    for i in 0..64 { tbl[TBL[i] as usize] = i as u8; }
    for (i, c) in v.bytes().filter_map(|c| { let c = tbl[c as usize]; if c < 64 { Some(c) } else { None } }).enumerate() {
        match i % 4 {
            0 => buf = c << 2,
            1 => { ret.push(buf | c >> 4); buf = c << 4; }
            2 => { ret.push(buf | c >> 2); buf = c << 6; }
            3 => ret.push(buf | c),
            _ => unreachable!(),
        }
    }
    ret
}

const TBL: &'static [u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
const BIN: &'static str = "<base64-encoded ELF executable removed>";