#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;

int main()
{
    int n, m; cin>>n>>m;
    if(n%2==0 && m%2==0) cout<<0<<endl;
    else if(n%2==0) cout<<n/4<<endl;
    else if(m%2==0) cout<<m/4<<endl;
    else cout<<n/4+m/4<<endl;
    return 0;
}