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)

#[allow(unused_macros)]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}
 
#[allow(unused_macros)]
macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};
 
    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
 
    ($next:expr, mut $var:ident : $t:tt $($r:tt)*) => {
        let mut $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}
 
#[allow(unused_macros)]
macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };
 
    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };
 
    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };
 
    ($next:expr, bytes) => {
        read_value!($next, String).into_bytes()
    };
 
    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };
 
    ($next:expr, $t:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}

fn main() {
    input! {
        cs: chars,
    }

    let mut kioku = 0;
    let ans = dfs(&cs, 0, &mut kioku);

    if let Some(ans) = ans {
        for i in 0..3 {
            print!("{}", cs[i]);
            if ans & 2usize.pow(i as u32) != 0  {
                print!("+");
            } else {
                print!("-");
            }
        }
        print!("{}", cs[3]);
        println!("=7");
    }       
}

fn dfs(cs: &Vec<char>, pos: usize, kioku: &mut usize) -> Option<usize>{
    if pos == 3 {
        let mut ans: i32= cs[0].to_digit(10).unwrap() as i32;
        for i in 1..4 {
            if *kioku & 2usize.pow(i-1) != 0 {
                ans = ans + cs[i as usize].to_digit(10).unwrap() as i32;
            } else {
                ans = ans - cs[i as usize].to_digit(10).unwrap() as i32;
            }
        }
        if ans == 7 {
            //println!("kioku: {}", *kioku);
            return Some(*kioku);
        } else {
            return None;
        }

    }

    let ret1 = dfs(cs, pos+1, kioku);
    *kioku = *kioku + 2usize.pow(pos as u32);
    let ret2 = dfs(cs, pos+1, kioku);
    *kioku = *kioku - 2usize.pow(pos as u32);

    if ret1.is_some() {
        return ret1; 
    } else if ret2.is_some() {
        return ret2;
    } else {
        return None;
    }
}