text: #include<bits/stdc++.h>
  #define ri register int
  #define mp make_pair
  using namespace std;
  typedef long long ll;
  const int INF=INT_MAX;
  inline int GetInt()
  {
      int num=0,bj=1;
      char c=getchar();
      while(!isdigit(c))bj=(bj==-1||c=='-')?-1:1,c=getchar();
      while(isdigit(c))num=num*10+c-'0',c=getchar();
      return num*bj;
  }
  int main()
  {
      //freopen(".in","r",stdin);
      //freopen(".out","w",stdout);
      int x=GetInt(),y=GetInt();
      int a=(x+y)/2,b=(x-y)/2;
      printf("%d\n",a*b);
      //fclose(stdin);
      //fclose(stdout);
      return 0;
  }