include [HTML_REMOVED]
using namespace std;
int main()
{
int x,y;
cin>>x>>y;
int sum=0;
if(y>x)swap(x,y);
int z=y+1;
for(z;z<x;z++){
if(z%2==1||z%2==-1){
sum+=z;
}
}
cout<<sum;
return 0;
}