//#define dxx
#ifdef dxx
#define dbg(...) fprintf(stderr,__VA_ARGS__)
#define dex(a) dbg(#a"=%lld onL%d infun %s\n",a,__LINE__,__FUNCTION__)
#include<cstdlib>
#define pause sys##tem("pause")
#define _GLIBCXX_DEBUG
#endif

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cstdlib>
#include<vector>

using ll=long long;
using std::max;
using std::min;
using std::abs;
template<class T> void cmax(T&a,T b){a=max(a,b);}
template<class T> void cmin(T&a,T b){a=min(a,b);}
template<class T> T sqr(T a){return a*a;}

namespace xm{
    void _(){
        int N,M,child;

        scanf("%d%d",&N,&M);
        child=(M+3)/4;
        printf("%d\n",2*(child*3>=N?child:child+(N-child*3+3-(child*4>M))/4)-1);
    }
}

int main(){
    xm::_();
    return 0;
}