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 C (Clang 3.8.0) (judge verdict: Wrong Answer)

#include<stdio.h>

int fun(int a, int* x)
{
	float b;
	int c;
	int t;
	c = a / 0.08;
	b = ((float)a) / 0.08;
	if (b == c)
		* x = c;
	else
		*x = c + 1;
	*(x + 1) = a / 0.1;
	if (*x > * (x + 1))
		t = *x, * x = *(x + 1), * (x + 1) = t;
}

int main()
{
	int a, b;
	long long int x[2], y[2];
	scanf("%d%d", &a, &b);
	fun(a, x);
	fun(b, y);
	if (x[1]<y[0] || x[0]>y[1])
	{
		printf("-1");
		return 0;
	}
	if ( x[0]> y[0])
		printf("%d", y[0]);
	else
		printf("%d", x[0]);
}