#include <iostream>
#include <algorithm>
using namespace std;

int main()
{
   long long int n1,n2,ans,flag;
    
    while(cin>>n1)
    {
        cin>>n2;
        flag=0;
        if(n1==n2)
        {
            cout<<n1<<endl;
            continue;
        }
    if(n1>n2)
        {
            swap(n1,n2);
        }
    if((n1<=0&&n2<=0))
        {
            flag=1;
            n1=abs(n1);
            n2=abs(n2);
            ans = ((n2*n2-n1*n1)+(n2-n1))/2;
            ans-=n2;
            cout<<ans<<endl;
        }
        else if((n1>=0&&n2>=0))
        {
             flag=0;
             n1=abs(n1);
             n2=abs(n2);
             ans = ((n2*n2-n1*n1)+(n2-n1))/2;
             ans+=n1;
             cout<<ans<<endl;
        }
        else
        {
            n1=abs(n1);
            n2=abs(n2);
            n1=(n1*(n1+1))/2;
            n2=(n2*(n2+1))/2;
            n1=-n1;
            ans=n1+n2;
            cout<<ans<<endl;
        }   
    }
return 0;
}