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("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 input: Vec<char> = read::<String>().chars().collect();
    let a: i16 = input[0] as i16 - 48;
    let b: i16 = input[1] as i16 - 48;
    let c: i16 = input[2] as i16 - 48;
    let d: i16 = input[3] as i16 - 48;
    let mut ans: [i16; 8] = [0; 8];

    // A ? B ? C ? D
    ans[0] = a + b + c + d;
    if ans[0] == 7 {
        println!("{}+{}+{}+{}=7", a, b, c, d);
        return;
    }
    ans[1] = a + b + c - d;
    if ans[1] == 7 {
        println!("{}+{}+{}-{}=7", a, b, c, d);
        return;
    }
    ans[2] = a + b - c + d;
    if ans[2] == 7 {
        println!("{}+{}-{}+{}=7", a, b, c, d);
        return;
    }
    ans[3] = a + b - c - d;
    if ans[3] == 7 {
        println!("{}+{}-{}-{}=7", a, b, c, d);
        return;
    }
    ans[4] = a - b + c + d;
    if ans[4] == 7 {
        println!("{}-{}+{}+{}=7", a, b, c, d);
        return;
    }
    ans[5] = a - b + c - d;
    if ans[5] == 7 {
        println!("{}-{}+{}-{}=7", a, b, c, d);
        return;
    }
    ans[6] = a - b - c + d;
    if ans[6] == 7 {
        println!("{}-{}-{}+{}=7", a, b, c, d);
        return;
    }
    ans[7] = a - b - c - d;
    if ans[7] == 7 {
        println!("{}-{}-{}-{}=7", a, b, c, d);
        return;
    }
}