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: Accepted)

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>

int Max(int a, int b){
	if(a > b){
		return a;
	}
	else{
		return b;
	}
}

int main(){
	int A,B;
	scanf("%d %d",&A,&B);
	int X;

	int B_min = B*10;
	int B_max = B*10 + 9;
	int A_min, A_max;
	if(A%2 == 0){
		A_min = 25*A/2;
		A_max = A_min + 12;
	}
	else{
		A_min = 25*A/2 + 1;
		A_max = A_min + 11;
	}

	// printf("X_A = %d X_B = %d\n",X_A,X_B);
	int i,j;
	for(int i=A_min; i<=A_max; i++){
		for(int j=B_min; j<=B_max; j++){
			if(i == j){
				printf("%d\n",i);
				return 0;
			}
		}
	} 
	printf("-1\n");

	return 0;
}