#include <iostream>
using namespace std;
long long a,b;
long long M(long long a,long long b) {
if(a>b) return a;
return b;
}
int main() {
cin >> a >> b;
a--;
a/=2;
a = M(a*(a+1)-2,0);
b/=2;
b = M(b*(b+1)-2,0);
cout<<b-a;
}