#include <bits/stdc++.h>
using namespace std;
#define int long long int

signed main() {
    int n, m;
    cin >> n >> m;
    int ans = 0;
    while (n > 0 || m > 0) {
        if (n >= 3 && m >= 3) {
            n -= 3;
            m -= 3;
            if (n > m) {
                --n;
            } else {
                --m;
            }
        } else if (n >= 3) {
            m = 0;
            n -= 4;
        } else if (m >= 3) {
            m -= 4;
            n = 0;
        } else {
            m = 0;
            n = 0;
        }
        ++ans;
    }
    cout << ans << endl;
    return 0;
}