#include <bits/stdc++.h>
using namespace std;
int main()
{
    int i,m,n,sum=0;
    scanf("%d %d",&m,&n);
    if(m%2==0)
    m++;
    for(i=m;i<=n;i+=2)
    sum+=i;
    printf("%d\n",sum);
    return 0;
}