#include<stdio.h>
#include<stdbool.h>
#include<math.h>
int main()
{
    int n, t, i, j, num;
    float a;
    bool lights[2000002] = {false};
    scanf("%d", &n);
    //模拟开关灯
    for(i = 0; i < n; i++)
    {
        scanf("%f %d", &a, &t);
        for(j = 1; j <= t; j++)
        {
            num = floor(a * j);
            lights[num] = !lights[num]; //改变状态
        }
    }
    //找开着的灯
    i=1;//从1开始找
    while(lights[i]==0)
    i++;
    printf("%d",i);
    return 0;
}