Algorithm

A. A Variety of Operations
time limit per test
1 second
memory limit per test
256 megabytes
problem link- https://codeforces.com/problemset/problem/1556/A
input
standard input
output
standard output

William has two numbers a� and b� initially both equal to zero. William mastered performing three different operations with them quickly. Before performing each operation some positive integer k� is picked, which is then used to perform one of the following operations: (note, that for each operation you can choose a new positive integer k�)

  1. add number k� to both a� and b�, or
  2. add number k� to a� and subtract k� from b�, or
  3. add number k� to b� and subtract k� from a�.

Note that after performing operations, numbers a� and b� may become negative as well.

William wants to find out the minimal number of operations he would have to perform to make a� equal to his favorite number c� and b� equal to his second favorite number d�.

Input

Each test contains multiple test cases. The first line contains the number of test cases t� (1≤t≤1041≤�≤104). Description of the test cases follows.

The only line of each test case contains two integers c� and d� (0≤c,d≤109)(0≤�,�≤109), which are William's favorite numbers and which he wants a� and b� to be transformed into.

Output

For each test case output a single number, which is the minimal number of operations which William would have to perform to make a� equal to c� and b� equal to d�, or −1−1 if it is impossible to achieve this using the described operations.

Example
input
Copy
6
1 2
3 5
5 3
6 6
8 0
0 0
output
Copy
-1
2
2
1
2
0
Note

Let us demonstrate one of the suboptimal ways of getting a pair (3,5)(3,5):

  • Using an operation of the first type with k=1�=1, the current pair would be equal to (1,1)(1,1).
  • Using an operation of the third type with k=8�=8, the current pair would be equal to (−7,9)(−7,9).
  • Using an operation of the second type with k=7�=7, the current pair would be equal to (0,2)(0,2).
  • Using an operation of the first type with k=3�=3, the current pair would be equal to (3,5)(3,5).

 

Code Examples

#1 Code Example with C++ Programming

Code - C++ Programming

#include<iostream>
using namespace std;

int main(){
  int n, p, q, count;
  cin>>n;
  for(int i = 0; i < n; i++){
    cin>>p;
    cin>>q;
    if((p+q)%2 != 0){
      cout<<-1<<endl;
    }
    else if(p == 0 && q == 0){
      cout<<0<<endl;
    }
    else if(p == q){
      cout<<1<<endl;
    }
    else{
      cout<<2<<endl;

    }

  }
  return 0;
}
Copy The Code & Try With Live Editor

Input

x
–
+
cmd
6
1 2
3 5
5 3
6 6
8 0
0 0

Output

x
–
+
cmd
-1
2
2
1
2
0
Advertisements

Demonstration

Codeforcess Solution 1556-A A. A Variety of Operations ,C++, Java, Js and Python,1556-A,Codeforcess Solution

Previous
Codeforces solution 1080-B-B. Margarite and the best present codeforces solution
Next
CodeChef solution DETSCORE - Determine the Score CodeChef solution C,C+