#include <iostream>
#include <algorithm>
using namespace std;
int main() {
int x, y;
cin >> x >> y;
if (x > y) {
int tmp = x;
x = y;
y = tmp;
}
int total = 0;
for (int i = ++x; i < y; i++) {
if (abs(i) % 2 == 1) {
total += i;
}
}
cout << total << endl;
return 0;
}