/*For today, you happen to be the defeated. But what will you become tomorrow?*/

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;

#define int long long int 
#define dbg if(debugg)
#define F first 
#define S second 

bool debugg = false;

template <typename T>
using order_set = tree<T, null_type,less<T>, rb_tree_tag,tree_order_statistics_node_update>;

template <typename T>
using minheap = priority_queue<T, vector<T>, greater<T>>;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());  
bool f(int mid, int n, int m)
{
	int x = max(0ll, n - 3 * mid) + max(0ll, m - 3 * mid);
	return x <= mid;
}
void solve()
{
    int n, m;
    cin >> n >> m;
    int lo = 0, hi = n + m, ans = 0;
    while(lo <= hi){
    	int mid = (lo + hi) / 2;
    	if(f(mid, n, m)){
    		ans = mid;
    		hi = mid - 1;
    	}
    	else lo = mid + 1;
    }
    cout << 2 * ans - 1 << '\n';
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
        
    int t = 1;
    // cin >> t;
    
    while(t--){
        solve();
    }

    return 0;
}