#include <iostream>
#include <cmath>
using namespace std;
int main()
{
int x,y;
cin >> x >> y;
if (x > y) {
swap(x,y);
}
int sum = 0;
for (int i = x + 1; i < y; i++) {
if ((i & 1)) {
sum += i;
}
}
cout << sum << endl;
return 0;
}