#include <iostream>

using namespace std;

int main() {
    int x, y;
    int sum = 0;
    cin >> x >> y;
    if (x > y) {
        int t = y;
        y = x;
        x = t;
    }
    for (int i = x + 1; i < y; i++) {
        if (i % 2 == 1 || i % 2 == -1 ) sum += i;
    }


    cout << sum << endl;
    return 0;
}