#include <bits/stdc++.h>
using namespace std;
#define int long long
int n,a[11],b[11],M=1,x,y,ans;
int exgcd(int q,int w)
{
	if (w==0)
	{
		x=1;
		y=0;
		return q;
	}
	int tmp=x;
	x=y;
	y=tmp-q/w*y;
	exgcd(w,q%w);
	return q;
}
signed main()
{
	cin>>n;
	for (int i=1;i<=n;i++)
	{
		cin>>a[i]>>b[i];
		M*=a[i];
	}
	for (int i=1;i<=n;i++)
	{
		ans+=exgcd(M/a[i],a[i])*(M/a[i])*b[i];
	}
	cout<<(ans%M+M)%M;
	return 0;
}