#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <complex>
#include <deque>
#include <forward_list>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <optional>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#ifdef RUTHEN_LOCAL
#include <debug.hpp>
#else
#define show(x) true
#endif

using namespace std;

#define REP(i, n) for (int i = 0; i < (n); i++)
#define rep(i,n) for (int i = 0; i< (n); i++)

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N,M; cin >> N >> M;
    int ok = N+M, ng = 0;
    while(abs(ok-ng)>1){
        int mid = (ok+ng)/2;
        int n = max(0,N-mid*3), m = max(0,M-mid*3);
        if(n+m<=mid) ok = mid;
        else ng = mid;
    }
    cout << ok*2-1 << endl;
    return 0;
}