//Vijos 1164

 #include<cstdio>

 #include<cstdlib>

 #include<cstring>

 #include<iostream>

 #include<algorithm>

 #define rep(i,n) for(int i=0;i<n;++i)

 #define F(i,j,n) for(int i=j;i<=n;++i)

 #define D(i,j,n) for(int i=j;i>=n;--i)

 using namespace std;

 int getint(){

     int v=,sign=; char ch=getchar();

     while(ch<''||ch>'') {if (ch=='-') sign=-; ch=getchar();}

     while(ch>=''&&ch<='') {v=v*+ch-''; ch=getchar();}

     return v*=sign;

 }

 typedef long long LL;

 /*******************tamplate********************/

 void exgcd(LL a,LL b,LL &d,LL &x,LL &y){

     if(!b){ d=a; x=; y=; }

     else { exgcd(b,a%b,d,y,x); y-=x*(a/b); }

 }

 LL china(int n,int *a,int *m){

     LL M=,d,y,x=;

     F(i,,n) M*=m[i];

     F(i,,n){

         LL w=M/m[i];

         exgcd(m[i],w,d,d,y);

         x=(x+y*w*a[i])%M;

     }

     return (x+M)%M;

 }

 int a[],b[];

 int main(){

     int n=getint();

     F(i,,n) a[i]=getint(),b[i]=getint();

     printf("%lld\n",china(n,b,a));

     return ;

 }