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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>

int main(void){
	int a;
	int b;
	int kouho1, kouho2;
	int kouho1_1, kouho1_2, kouho2_1, kouho2_2;
	int flag = 0;

	scanf("%d %d", &a, &b);
	
	kouho1 = a*100/8;
	kouho2 = b*100/10;

	kouho1_1 = kouho1*0.08;
	kouho1_2 = kouho1*0.1;

	kouho2_1 = kouho2*0.08;
	kouho2_2 = kouho2*0.1;
	
	if ((a==kouho1_1)&&(b==kouho1_2)) {
		printf("%d ", kouho1);
		flag = 1;
	} 
	if ((a==kouho2_1)&&(b==kouho2_2)) {
		if(kouho1 != kouho2){ printf("%d", kouho2); }
		flag = 1;
	}
	if (flag == 0) {
		printf("-1");
	}
	puts("");

	return 0;
}