#include <cstdio>

int main()
{
	int n, m, k;
	scanf( "%d %d", &n, &m );
	
	k = 0;
	while ( ( ( n >= 1 ) && ( m >= 2 ) ) || ( (m>=1) && (n>=2) ) )
	{
		if ( n > m )
		{
			n-=2;
			m-=1;
			k+=2;
		}
		else
		{
			n-=1;
			m-=2;
			k+=2;
		}
	}
	printf( "%d\n", k );
}
