#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define OPFI(x) freopen(#x".in", "r", stdin);\
                freopen(#x".out", "w", stdout)
#define REP(i, a, b) for(int i=(a); i<=(b); ++i)
#define REPd(i, a, b) for(int i=(a); i>=(b); --i)
inline ll rd(){
    ll r=0, k=1; char c; while(!isdigit(c=getchar())) if(c=='-') k=-k;
    while(isdigit(c)) r=r*10+c-'0', c=getchar(); return r*k;
}
ll n, m, ans;
bool check(ll x){
    ll a=n, b=m;
    a-=x*3, b-=x*3;
    if(a<0) a=0;
    if(b<0) b=0;
    return a+b<=x;
}
int main(){
    n=rd(), m=rd();
    ll l=1, r=1e6;
    while(l<=r){
        ll mid=(l+r)/2;
        if(check(mid)){
            r=mid-1;
            ans=mid;
        }else l=mid+1;
    }
    printf("%lld\n", 2*ans-1);
    return 0;
}