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