/*
 * =========================================================
 *
 * 	Task: Light
 * 	User: Fanzeyi
 * 	Lang: C
 *
 * =========================================================
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int n;

int main()
{
	FILE *fin=fopen("light.in","r");
	int i,j;
	double *a;
	int *t;
	short *light;
	long num=0;
	int c;
	fscanf(fin,"%d",&n);
	a=(double*)malloc(sizeof(double)*n);
	t=(int*)malloc(sizeof(int)*n);
	for(i=0;i<n;i++)
	{
		fscanf(fin,"%lf %d",&a[i],&t[i]);
		num+=(int)a[i]*t[i];
	}
	light=(short*)malloc(sizeof(short)*(num+1));
	memset(light,0,num*sizeof(short));
	for(i=0;i<n;i++)
	{
		for(j=0;j<t[i];j++)
		{
			c=(int)(j+1)*a[i];
			if(light[c]==1)
				light[c]=0;
			else
				light[c]=1;
		}
	}
	for(i=0;i<num;i++)
		if(light[i]==1)
		{
			printf("%d",i);
			break;
		}
	return 0;
}