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;

pub 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")
}

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

  if a + b + c + d == 7 {
    println!("{}+{}+{}+{}=7", a, b, c, d);
  } else if a + b + c - d == 7 {
    println!("{}+{}+{}-{}=7", a, b, c, d);
  } else if a + b - c + d == 7 {
    println!("{}+{}-{}+{}=7", a, b, c, d);
  } else if a - b + c + d == 7 {
    println!("{}-{}+{}+{}=7", a, b, c, d);
  } else if a - b - c + d == 7 {
    println!("{}-{}-{}+{}=7", a, b, c, d);
  } else if a + b - c - d == 7 {
    println!("{}+{}-{}-{}=7", a, b, c, d);
  } else if a - b + c - d == 7 {
    println!("{}-{}+{}-{}=7", a, b, c, d);
  } else if a - b - c - d == 7 {
    println!("{}-{}-{}-{}=7", a, b, c, d);
  }
}