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 Go (1.6) (judge verdict: Wrong Answer)

package main

import (
	"fmt"
)

func main() {
	sA, sB := 0.08, 0.1

	A, B := readInt(), readInt()
	gA, gB := int(float64(A)/sA), int(float64(B)/sB)
	rAA, rAB, rBA, rBB := int(float64(gA)*sA), int(float64(gA)*sB), int(float64(gB)*sA), int(float64(gB)*sB)
	cA, cB := rAA == A && rAB == B, rBA == A && rBB == B
	
	if cA && cB {
		fmt.Println(min(gA, gB))
	} else if cA {
		fmt.Println(gA)
	} else if cB {
		fmt.Println(gB)
	} else {
		fmt.Println(-1)
	}

}

func readInt() int {
	var v int
	fmt.Scan(&v)
	return v
}

func min(a, b int) int {
	if a >= b {
		return b
	} else {
		return a
	}
}