Problem:
Score : 300 points

Problem Statement

Find the price of a product before tax such that, when the consumption tax rate is 8 percent and 10 percent, the amount of consumption tax levied on it is A yen and B yen, respectively. (Yen is the currency of Japan.)

Here, the price before tax must be a positive integer, and the amount of consumption tax is rounded down to the nearest integer.

If multiple prices satisfy the condition, print the lowest such price; if no price satisfies the condition, print -1.

Constraints

1 \leq A \leq B \leq 100

A and B are integers.

Input

Input is given from Standard Input in the following format:

A B

Output

If there is a price that satisfies the condition, print an integer representing the lowest such price; otherwise, print -1.

Sample Input 1

2 2

Sample Output 1

25

If the price of a product before tax is 25 yen, the amount of consumption tax levied on it is:

When the consumption tax rate is 8 percent: \lfloor 25 \times 0.08 \rfloor = \lfloor 2 \rfloor = 2 yen.

When the consumption tax rate is 10 percent: \lfloor 25 \times 0.1 \rfloor = \lfloor 2.5 \rfloor = 2 yen.

Thus, the price of 25 yen satisfies the condition. There are other possible prices, such as 26 yen, but print the minimum such price, 25.

Sample Input 2

8 10

Sample Output 2

100

If the price of a product before tax is 100 yen, the amount of consumption tax levied on it is:

When the consumption tax rate is 8 percent: \lfloor 100 \times 0.08 \rfloor = 8 yen.

When the consumption tax rate is 10 percent: \lfloor 100 \times 0.1 \rfloor = 10 yen.

Sample Input 3

19 99

Sample Output 3

-1

There is no price before tax satisfying this condition, so print -1.

Solution in Rust (1.15.1) (judge verdict: Accepted)

#![allow(dead_code)]
#![allow(unused_variables)]
#![allow(unused_imports)]

use std::io::stdin;
use std::str::FromStr;
use std::cmp::min;
use std::process::exit;

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

fn read_vec<T: FromStr>() -> Vec<T> {
    let mut str = String::new();
    stdin().read_line(&mut str).ok();
    str.trim().split_whitespace().map(|e| e.parse().ok().unwrap()).collect()
}

fn read_n_vec<T: FromStr>(n: u64) -> Vec<Vec<T>> {
    let mut v_outer = Vec::new();
    for _ in 0..n {
        let v_inner = read_vec();
        v_outer.push(v_inner);
    }
    v_outer
}

fn main() {
    let line: Vec<u32> = read_vec();
    let a = line[0];
    let b = line[1];

    for i in 1..1251 {
        if (i as f32 * 0.08) as u32 == a && (i as f32 * 0.1) as u32 == b {
            println!("{}", i);
            exit(0);
        }
    }
    println!("-1");
}