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 (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	var input = irLine(1)
	var A, B = float64(input[0][0]), float64(input[0][1])

	var a int = int(A / 8.00 * 100.00)

	// fmt.Printf("A:%f B:%f a:%d\n", A, B, a)

	var b int = a

	for i := 0; ; b-- {
		if int(float64(b)/100.0*10.0) < int(B) {
			if i > 0 {
				b++
			}
			break
		}
		i++
	}

	if int(float64(b)*8.0/100.0) != int(A) {
		fmt.Printf("-1")
		return
	}

	fmt.Printf("%d", b)
	return
}

func minf(a, b float64) float64 {
	if a > b {
		return b
	}
	return a
}

func mini(a, b int) int {
	if a > b {
		return b
	}
	return a
}

func paw(f float64, num int) float64 {
	var result float64
	for i := 0; num > i; i++ {
		result *= result
	}
	return result
}

//StrStdin Read standard input data
func StrStdin(line int) [][]string {
	var stringInput [][]string
	scanner := bufio.NewScanner(os.Stdin)

	for i := 0; i < line; i++ {
		scanner.Scan()
		if s := scanner.Text(); s != "" {
			stringInput = append(stringInput, strings.Split(strings.TrimSpace((scanner.Text())), " "))
		} else {
			break
		}
	}

	return stringInput
}

//rLine Read standard input data
func rLine(line int) [][]string {
	var rdr = bufio.NewReaderSize(os.Stdin, 1000000)
	var buf = make([]byte, 0, 1000000)
	var stringInput [][]string

	for i := 0; i < line; {
		l, p, e := rdr.ReadLine()
		if e != nil {
			panic(e)
		}
		buf = append(buf, l...)
		if !p {
			stringInput = append(stringInput, strings.Split(strings.TrimSpace((string(buf))), " "))
			buf = []byte{}
			i++
		}
	}
	return stringInput
}

func irLine(i int) [][]int {
	return alitoas(rLine(i))
}

//itoa converts string to integer
func itoa(s string) int {
	var i, _ = strconv.Atoi(s)
	return i
}

func itoas(S []string) []int {
	var result = make([]int, len(S))
	for i, s := range S {
		result[i] = itoa(s)
	}
	return result
}

func alitoas(S [][]string) [][]int {
	var result = make([][]int, len(S))
	for i, s := range S {
		result[i] = itoas(s)
	}
	return result
}

func gcd(a, b int) int {
	if b == 0 {
		return a
	}
	return gcd(b, a%b)
}

func gcd3(a, b, c int) int {
	return gcd(gcd(a, b), c)
}