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

//--------------------------------
// #define int long long
#define LL long long
// #define lc p << 1
// #define rc p << 1 | 1
#define lowbit(x) x & (-x)
#define nc() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 100000, stdin), p1 == p2) ? EOF : *p1++)
// #pragma GCC optimize(2)
#define Blizzard ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)

inline void read(LL &a)
{
    LL s = 0, w = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9')
    {
        if (ch == '-')
            w = -1;
        ch = getchar();
    }
    while (ch >= '0' && ch <= '9')
    {
        s = s * 10 + ch - '0';
        ch = getchar();
    }
    a = s * w;
}
//-----------------------------------------
void solve()
{
    int n, m;
    cin >> n >> m;
    if (n == 0 && m == 0)
    {
        cout << 0;
        return;
    }
    int k1 = 0, k2 = 0;
    k1 = n / 4;
    k1 += ((n % 4 == 0) ? 0 : 1);
    int t = n % 4;
    if (t)
        m = m - k1 * 3 - t - (4 - t);
    else
        m = m - k1 * 3;

    if (m <= 0)
    {
        cout << 2 * k1 - 1;
        return;
    }
    else
    {
        // cout << m << endl;
        k2 = m / 4;
        if (m % 4)
            k2++;
        // cout << k1 << " " << k2 << endl;
        cout << (k2 + k1) * 2 - 1;
    }
}

signed main()
{
    Blizzard; // false
    int _ = 1;
    // cin >> _;
    while (_--)
        solve();
    return 0;
}
/*
while (l < r)
    {
        int mid = l + r >> 1;
        if (check(mid)) r = mid;
        else l = mid + 1;
    }
*/