#include <iostream>

using namespace std;

int main()
{
     int x, y;
     cin >> x >> y;
     int sum = 0;

     if (x > y)
     {
         int t;
         t = x;
         x = y;
         y = t;
     }

     for (int i = 1; i <=(y - x) ; i++)
     {
         if ( x%2) 
         {
             while (x < y -2)
             {
                 x += 2;
                 sum += x;
             }
         }
         else 
         {
             x = x - 1;
             while (x < y-2)
             {
                 x += 2;
                 sum += x;
             }
         }
     }
     cout << sum << endl;
     return 0;
}