# include <fstream.h>
int  main()
{unsigned long n,k,j,poz=0,v[10]; int d; for(k=1;k<=7;k++) v[k]=0;
ifstream fin("pascal.in");
fin>>n>>d;  fin.close();
for(k=1;k<=n/2+1;k++)
 { for (j=2;j<=6;j++)
 {if((n-k+1)%j==0)  v[j]++;
  if(k%j==0)  v[j]--;}
  if(v[2]>1) v[4]=2;if(v[2]>=1 && v[3]>=1) v[6]=2;
     if(v[d]>=1) poz=k;k=n/2+2;}
 ofstream fout("pascal.out");
  if(poz!=0) fout<<(n+1)-2*poz;else fout<<0; fout.close();
return 0;
}