#include<iostream>
#include<fstream>
#include<string.h>

using namespace std;

bool b[5000];
int d1,d2,d3,d4;
long a,s,f;
double st;




void ms(double st1,int i2)
{  
	double sst;
	for (d2=1;d2<=i2;d2++)
	{
		sst=d2*st1;
		if (b[int(sst)]==0) {b[int(sst)]=1;} 
		else 
			if  (b[int(sst)]==1) {b[int(sst)]=0;};
			
	}
	
	
	
};

void mn()
{
	for (d3=1;d3<=5000;d3++)
	{
		if (b[d3]==1) return;
	}
};

	
	
	



int main()
{
	memset(b,0,sizeof(b));
	ifstream fin("light.in");
	ofstream fout("light.out");
	fin>>a;
	for (d1=1;d1<=a;d1++)
	{
		fin>>st>>s;
		ms(st,s);

	}
	
     mn();		
	fout<<d3<<endl;
		
		
			
	return 0;
}