#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
    int i,x,y,count=0;
    cin>>x>>y;
    if(x<y)
    {
        for(i=x+1;i<y;i++)
        {
            if(i%2!=0)count+=i; 
        }
    }
    else
    {
        for(i=y+1;i<x;i++)
        {
            if(i%2!=0)count+=i; 
        }
    }
    cout<<count<<endl;
    return 0;
}