#include <iostream>
using namespace std;
int main(){
    int n, m, all = 0;
    cin >> m >> n;
    if(n % 2 == 0) m ++;
    if(m % 2 == 0) n--;
    for(int i = m;i <= n; i += 2)all += i;
    cout << all;
    return 0;
}