#include<bits/stdc++.h>
using namespace std;
int main()
{
int m,n,sum=0;
cin>>m>>n;
if(m%2==0)
m+=1;
if(n%2==0)
n-=1;
for(int i=m;i<=n;i+=2)
{
sum+=i;
}
cout<<sum;
}