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)

use std::io;
use std::collections::HashMap;
fn main() {
	let mut buf = String::new();
	io::stdin().read_line(&mut buf).expect("");
	let mut iter = buf.split_whitespace();
	let a:i32 = match iter.next().unwrap().parse() {
		Ok(n) => n,
		Err(_) => panic!(""),
	};
	let b: i32 = match iter.next().unwrap().parse() {
		Ok(n) => n,
		Err(_) => panic!(""),
	};
	let mut tax:HashMap<(i32, i32), Vec<i32>> = HashMap::new();
	for i in (1..1010) {
		
			let mut m = tax.insert((i*8/100, i*10/100), vec![]);
			if m == None {
				let mut v = vec![i];
				tax.insert((i*8/100, i*10/100), v);
			}else{
				let mut v = m.unwrap();
				v.push(i);
				tax.insert((i*8/100, i*10/100), v);
			}
		
	}
	match tax.get(&(a, b)) {
		None => println!("-1"),
		Some(v) => println!("{}", v[0]),
	};
}