#include<stdio.h>
int main()
{
    int n, i,j, a[100], b[100],k=0,g=1;
    scanf("%d\n", &n);
    for (i = 0; i < n; i++)
        scanf("%d %d", &a[i], &b[i]);
    int x[100];
    for (j = 0; j < n; j++)
    {
        int i,g=1;
        for (i = 0; i < n; i++)
        {
            if (i==j)
                continue;
            else
                g = g * a[i];
        }
        int t;
        for (t = 1;; t++)
        {
            if ((g * t - 1) % a[j] == 0)
                break;
        }
        x[j] = g * t;
    }
    for (int m = 0; m < n; m++)
        k = k + x[m] * b[m];
    for (int m = 0; m < n; m++)
        g = g * a[m];
    if (k > g)
        k = k - g;
    printf("%d", k);
    return 0;
}