84pts
data:link
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1e6+10;
int n;
ll ai[N],mi[N];
ll exgcd(ll a,ll b,ll &x,ll &y)
{
if(!b) {x=1,y=0; return a;}
else
{
ll d=exgcd(b,a%b,y,x);
y-=a/b*x;
return d;
}
}
ll qmul(ll a,ll k,ll mod)//龟速乘
{
ll res=0;
while(k>0)
{
if(k&1) res=(res%mod+a%mod)%mod;
a=(a%mod+a%mod)%mod;
k>>=1;
}
return (res%mod+mod)%mod;
}
void excrt()
{
bool flag=1;//是否有解
ll a1=ai[1],m1=mi[1];
for(int i=2;i<=n;i++)
{
ll a2=ai[i],m2=mi[i];
ll k1,k2;
ll d=exgcd(m1,-m2,k1,k2);
if((a2-a1)%d!=0)//无解
{
flag=0;
break;
}
ll t=m2/d;
k1=qmul(k1,(a2-a1)/d,t);
a1=m1*k1+a1;
m1=(m1/d*m2>0?m1/d*m2:-(m1/d*m2));
}
if(flag) printf("%lld",(a1%m1+m1)%m1);
else printf("-1");
}
int main()
{
#ifdef test
freopen("P4777_15.in","r",stdin);
#endif
scanf("%d",&n);
for(int i=1;i<=n;i++)
scanf("%lld%lld",&mi[i],&ai[i]);
excrt();
return 0;
}