#include <iostream>

using namespace std;

int main()// 看清题意
{
    int a, b;
    cin >> a >> b;

    if (a > b) 
    {
        int t = a;
        a = b;
        b = t;
    }

    int ans = 0;
    for (int i = a + 1; i < b; i++)
    {
        //cout << "i = " << i << endl;
        if(i % 2 != 0) ans += i;
        //cout << ans << endl;
    }
    cout << ans << endl;

    return 0;
}