#include<bits/stdc++.h>
using namespace std;
int main()
{
int a,b;
int sum=0;
int i;
cin>>a>>b;
if(a%2==0) a++;
for(i=a;i<=b;i+=2)
sum+=i;
cout<<sum<<endl;
return 0;
}
#include<bits/stdc++.h>
using namespace std;
int main()
{
int a,b;
int sum=0;
int i;
cin>>a>>b;
if(a%2==0) a++;
for(i=a;i<=b;i+=2)
sum+=i;
cout<<sum<<endl;
return 0;
}