1 //Vijos 1164
 2 #include<cstdio>
 3 #include<cstdlib>
 4 #include<cstring>
 5 #include<iostream>
 6 #include<algorithm>
 7 #define rep(i,n) for(int i=0;i<n;++i)
 8 #define F(i,j,n) for(int i=j;i<=n;++i)
 9 #define D(i,j,n) for(int i=j;i>=n;--i)
10 using namespace std;
11 
12 int getint(){
13     int v=0,sign=1; char ch=getchar();
14     while(ch<‘0‘||ch>‘9‘) {if (ch==‘-‘) sign=-1; ch=getchar();}
15     while(ch>=‘0‘&&ch<=‘9‘) {v=v*10+ch-‘0‘; ch=getchar();}
16     return v*=sign;
17 }
18 typedef long long LL;
19 /*******************tamplate********************/
20 
21 void exgcd(LL a,LL b,LL &d,LL &x,LL &y){
22     if(!b){ d=a; x=1; y=0; }
23     else { exgcd(b,a%b,d,y,x); y-=x*(a/b); }
24 }
25 LL china(int n,int *a,int *m){
26     LL M=1,d,y,x=0;
27     F(i,1,n) M*=m[i];
28     F(i,1,n){
29         LL w=M/m[i];
30         exgcd(m[i],w,d,d,y);
31         x=(x+y*w*a[i])%M;
32     }
33     return (x+M)%M;
34 }
35 int a[11],b[11];
36 int main(){
37     int n=getint();
38     F(i,1,n) a[i]=getint(),b[i]=getint();
39     printf("%lld\n",china(n,b,a));
40     return 0;
41 }