Problem:
Score : 100 points

Problem Statement

In K-city, there are n streets running east-west, and m streets running north-south. Each street running east-west and each street running north-south cross each other. We will call the smallest area that is surrounded by four streets a block. How many blocks there are in K-city?

Constraints

2 ≤ n, m ≤ 100

Input

Input is given from Standard Input in the following format:

n m

Output

Print the number of blocks in K-city.

Sample Input 1

3 4

Sample Output 1

6

There are six blocks, as shown below:

Sample Input 2

2 2

Sample Output 2

1

There are one block, as shown below:

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
int main(){
  long N;
  long two = 0;
  long four = 0;
  scanf("%lld",&N);
  vector <long> num(N);
  for(int i = 0;i<N;i++){
    scanf("%d", &num.at(i));
  }
  for(int i = 0;i<N;i++){
    if(num.at(i)%2 == 0){
      two++;
    }
    if(num.at(i)%4 == 0){
      two--;
      four++;
    }
  }
  if(N <= 2*four+two || N <= 2*four+1){
    printf("%s","Yes");
  }
  else{
    printf("%s","No");
  }
  return 0;
}