#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define endl '\n';


bool comp(pair<int,int>a,pair<int,int>b){
    if(a.first == b.first){
        return a.second < b.second;
    }

    return a.first > b.first;
}


void tc(){
    int t;
    cin >> t;
    while (t--){

        

    }
  
}


int main()
{

    ios::sync_with_stdio(0);
    cin.tie(0);

    //tc();

    ll x,y;
    cin >> x >> y;

    ll mn = min(x,y);



    ll i = 1;

    ll ans = 0;

    while (i <= mn){

        ans += (x*y);
        --x;
        --y;
        ++i;

        
    }

    cout << ans << endl;
    

    


    return 0;
}