#include <iostream>
using namespace std;
typedef unsigned long long ll;
int n;
int m[15],a[15];
ll mul[15];
ll xx;
void CRT()
{
    for(int i = 1;i <= n;i ++)
    {
        ll temp = mul[n] / m[i];
        ll h = mul[n] / m[i];
        while(true)
        {
            if(temp % m[i] == 1) break;
            temp += h;
        }
        xx += (a[i] * temp) % mul[n];
    }
    cout << xx % mul[n];
}
int main()
{
    cin >> n;
    mul[0] = 1; // 前缀积 
    for(int i = 1;i <= n;i ++)
    {
        cin >> m[i] >> a[i];
        mul[i] = mul[i - 1] * m[i];
    }
    CRT();
    return 0;
}