#include<iostream>

 #include<cstring>

 #include<cstdio>

 #include<cmath>

 #include<algorithm>

 using namespace std;

 const long long N=;

 long long n,x,y,a[N],b[N],m,ans;

 long long exgcd(long long a,long long b,long long &x,long long &y){

     if(b==){

         x=;y=;

         return a;

     }

     long long tmp=exgcd(b,a%b,x,y);

     long long z=x;

     x=y;y=z-(a/b)*y;

     return tmp;

 }

 int main(){

     scanf("%lld",&n);

     m=;

     for(long long i=;i<=n;i++){

         scanf("%lld%lld",&a[i],&b[i]);

         m*=a[i];

     }

     for(long long i=;i<=n;i++){

         x=y=;

         exgcd(a[i],m/a[i],x,y);

         ans+=(m/a[i])*b[i]*y;

     }

     ans=(ans%m+m)%m;

     printf("%lld",ans);

     return ;

 }