#include<iostream>
//#include<cmath>
//#include<algorithm>
using namespace std;
int main()
{
int x, y;
int ans = 0;
cin >> x >> y;
if (x > y) swap(x, y);//交换x,y的位置
for (int i = x + 1 ; i < y ; i ++)
{
if (i % 2) ans += i;
}
cout << ans;
return 0;
}