#include<iostream>

using namespace std;

int main()

{

int a,b;

while(cin>>a>>b)

{

if(a>b){int t=a; a=b; b=t; }

    int sum=0;

    for(int i=a; i<=b; ++i) if(i%2==0) sum+=i;

    cout<<sum<<endl;

}

}