#include<stdio.h>
using namespace std;
int pom(int port, int ban)
{pas:
 if(ban>=1&&port>=1)
  port--;
 
 if(ban==0 && port!=1)
  port-=1;
   
  
 if(port==0 && ban!=1)
   {ban-=2;
    port++;}
 
 if(!(ban==0&&port==1))
  if(!(port==0&&ban==1))
  goto pas;
if(ban==1) return ban;
else return 0;
}

int main()
{short int t,i;
int b,p;
 FILE *f=fopen("fructe.in","r"), *g=fopen("fructe.out","w");
 
 fscanf(f,"%hd",&t);
  for(i=1;i<=t;i++)
	{fscanf(f,"%d%d", &b,&p);
	  fprintf(g,"%d\n",pom(b,p));
    }
fclose(f);
fclose(g);
return 0;
}