#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
int main(){
    int x,y;
    int ans=0;
    cin>>x>>y;
    if(x>y) swap(x,y);
    for(int i=x+1;i<y;i++){
        if(i%2) ans+=i;
    }
    printf("%d\n",ans);
    return 0;
}