#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll n,a[100005],m[100005];
//ax+by=gcd(a,b);
//x=y1,y=x1-a/b*y1;
void exgcd(ll a,ll b,ll &x,ll &y,ll &c)
{
    if(!b){
        x=1; y=0; c=a;
        return;
    }
    exgcd(b,a%b,y,x,c);
    y-=a/b*x;
}
ll China()
{
    ll x,y,c,lcm=1,ans=0;
    for(int i=1;i<=n;i++)
        lcm*=m[i];
    for(int i=1;i<=n;i++)
    {
        exgcd(lcm/m[i],m[i],x,y,c);
        x=(x%m[i]+m[i])%m[i];
        ans=(ans+x*lcm/m[i]*a[i])%lcm;
    }
    return (ans+lcm)%lcm;
}
int main()
{
    while(cin>>n){
        for(int i=1;i<=n;i++)cin>>m[i]>>a[i];
        cout<<China()<<endl;
    }
    return 0;
}