#include<bits/stdc++.h>
using namespace std;
int main()
{
    int i,n,m,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;
}