output_description: Print the minimum possible value of S_{max} - S_{min}.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      H W
attempt: #include <bits/stdc++.h>
  #define REP(i, n) for(int i = 0;i < n;i++)
  #define SORT(v, n) sort(v, v+n);
  #define VSORT(v) sort(v.begin(), v.end())
  #define VRSORT(v) sort(v.rbegin(), v.rend())//vectorの降順ソート
  #define ll long long
  #define pb(a) push_back(a)
  #define INF 1000000000
  #define MOD 1000000007
  using namespace std;
  typedef pair<int, int> P;
  typedef pair<ll, ll> LP;
  typedef pair<int, P> PP;
  typedef pair<ll, LP> LPP;
  
  typedef vector<unsigned int>vec;
  typedef vector<vec> mat;
  typedef tuple<ll, ll, ll> T;
  
  int dy[]={0, 0, 1, -1, 0};
  int dx[]={1, -1, 0, 0, 0};
  
  int main(){
      cin.tie(0);
      ios::sync_with_stdio(false);
      ll H,W;
      cin>>H>>W;
      ll a=0,b=0,c=0;//3つの長方形
  
      int mw = W / 2;
      ll ans = 1e12;
  
      for(int k=0;k<2;k++){
          for(int i=1;i<H;i++){
              a = i*W;
              int mh = (H-i) / 2;
  
              for(int j=0;j<2;j++){
                  if(j==0){//横２つに分割
                      b = (H-i) * mw;
                      c = (H-i) * (W-mw);
                  }
                  else{
                      b = mh * W;
                      c = (H-i-mh) * W;
                  }
                  ll ma = max({a,b,c});
                  ll mi = min({a,b,c});
  
                  ans = min(ans,ma-mi);
              }
          }
          swap(H,W);
      }
      cout<<ans<<endl;
  }
problem_description: Statement
  
  There is a bar of chocolate with a height of H blocks and a width of W blocks.
  Snuke is dividing this bar into exactly three pieces. He can only cut the bar
  along borders of blocks, and the shape of each piece must be a rectangle.
  
  Snuke is trying to divide the bar as evenly as possible. More specifically, he
  is trying to minimize S_{max} \- S_{min}, where S_{max} is the area (the
  number of blocks contained) of the largest piece, and S_{min} is the area of
  the smallest piece. Find the minimum possible value of S_{max} - S_{min}.
samples: [{"input": "3 5", "output": "0\n    \n\nIn the division below, S_{max} - S_{min} = 5 - 5 = 0.\n\n![2a9b2ef47b750c0b7ba3e865d4fb4203.png](https://atcoder.jp/img/arc074/2a9b2ef47b750c0b7ba3e865d4fb4203.png)\n\n* * *"}, {"input": "4 5", "output": "2\n    \n\nIn the division below, S_{max} - S_{min} = 8 - 6 = 2.\n\n![a42aae7aaaadc4640ac5cdf88684d913.png](https://atcoder.jp/img/arc074/a42aae7aaaadc4640ac5cdf88684d913.png)\n\n* * *"}, {"input": "5 5", "output": "4\n    \n\nIn the division below, S_{max} - S_{min} = 10 - 6 = 4.\n\n![eb0ad0cb3185b7ae418e21c472ff7f26.png](https://atcoder.jp/img/arc074/eb0ad0cb3185b7ae418e21c472ff7f26.png)\n\n* * *"}, {"input": "100000 2", "output": "1\n    \n\n* * *"}, {"input": "100000 100000", "output": "50000"}]