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;

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("filed 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 s: String = read();
    let arr: Vec<i32> = s.chars().map(|c| c.to_digit(10).unwrap() as i32).collect();
    for bit in 0..1 << 4 {
        let mut p_or_m = vec!["-"; 3];
        for i in 0..3 {
            if bit & (1 << i) != 0 {
                p_or_m[3 - 1 - i] = "+"
            }
        }
        let mut sum = arr[0];
        let mut ans = String::new();
        for j in 0..3 {
            ans += &arr[j].to_string();
            ans += p_or_m[j];
            if p_or_m[j] == "+" {
                sum += arr[j + 1];
            } else {
                sum -= arr[j + 1];
            }
        }
        ans += &arr[3].to_string();

        if sum == 7 {
            println!("{}=7", ans);
            break;
        }
    }
}