#include <iostream>
using namespace std;
int main()
{
int X, Y, Z;
int sum = 0;
cin >> X >> Y;
if (X > Y)
{
Z = X;
X = Y;
Y = Z;
}
for (int i = X + 1; i < Y; i++)
{
if (i % 2)
sum += i;
}
cout << sum << endl;
return 0;
}