#include<iostream>
using namespace std;
int main()
{
    int x,y,z;
    int sum=0;
    cin>>x>>y;
    if(x>y)swap(x,y);
    for(int i=x+1;i<=y-1;i++){
        if(i%2==0)continue;
        sum=sum+i;
    }
    cout<<sum;
    return 0;
}