#include <iostream>
#include<stdio.h>
#include<vector>
using namespace std;
 
int main() {
	// your code goes here
	int T;
	scanf("%d",&T);
	int prime[10000]={0};
	prime[0] = 1;
	prime[1] = 1;
	for(int i = 2 ;i<10000;i++)
	{
		if(prime[i] == 0)
		{
			for(int j = 2 ;i*j<10000;j++)
			prime[i*j] = 1;
		}
	}
	while(T--)
	{
		int a,b;
		scanf("%d%d",&a,&b);
		for(int i = 1;i<10000;i++)
		{
			if(prime[i+a+b] == 0)
			  {
			  	printf("%d\n",i);
			  	break;
			  }
 
		}
	}
	return 0;
}

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MgoxIDMKMTAwMCAxMDAw

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1 3
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