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::vec::Vec;

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>().split_whitespace().map(|e| e.parse().ok().unwrap()).collect()
}

fn main() {
  let cs: Vec<char> = read::<String>().chars().collect();
  let a: i64 = cs[0].to_digit(10).unwrap() as i64;
  let b: i64 = cs[1].to_digit(10).unwrap() as i64;
  let c: i64 = cs[2].to_digit(10).unwrap() as i64;
  let d: i64 = cs[3].to_digit(10).unwrap() as i64;

  for i in 0..2 {
    for j in 0..2 {
      for k in 0..2 {
        let (first_op, op1) = select_operator(i);
        let (second_op, op2) = select_operator(j);
        let (third_op, op3) = select_operator(k);
        let val: i64 = third_op(second_op(first_op(a, b), c), d);
        if val == 7 {
          println!("{}{}{}{}{}{}{}=7", a, op1, b, op2, c, op3, d);
          return;
        }
      }
    }
  }
}

fn select_operator(num: usize) -> (Box<Fn(i64, i64) -> i64>, char) {
    match num {
      0 => (Box::new(|x, y| { x + y }), '+'),
      1 => (Box::new(|x, y| { x - y }), '-'),
      _ => panic!(),
    }
}