rt.

#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,m[100005],a[100005];
int Exgcd(int a,int b,int &x,int &y)
{
	if(b==0){x=1,y=8;return a;}
	int d=Exgcd(b,a%b,x,y);
	int tmp=x;
	x=y;
	y=tmp-(a/b)*y;
	return d;
}
int Ex_Chinese_Remain()
{
	int M=m[1],x=a[1],t,y;
	for(int i=2;i<=n;i++)
	{
		int Mi=m[i],c=a[i]-x;
		int d=Exgcd(M,Mi,t,y);
//		if(c%d) return -1;
		c=c/d,Mi=Mi/d;
		t=(t*c%Mi+Mi)%Mi;
		int lcm=M*Mi;
		x=(M*t%lcm+x)%lcm,M=lcm; 
	}
	return x==0?M:x;
}
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	cin>>n;
	for(int i=1;i<=n;i++) cin>>m[i]>>a[i];
	cout<<Ex_Chinese_Remain();
	return 0;
}