#include<bits/stdc++.h>
using namespace std;
int n,di[11],rem[11];
unsigned long long lcm=1,ans,tmp[11];
int main(){
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		scanf("%d %d",&di[i],&rem[i]);
		lcm*=di[i];
	}
	//printf("%d\n",lcm);
	for(int i=1;i<=n;i++){
		tmp[i]=lcm/di[i];
		//printf("tmp[%d]=%d\n",i,tmp[i]);
	}
	for(int i=1;i<=n;i++){
		for(unsigned long long j=1;;j++){
			if((j*tmp[i])%di[i]==1){
				ans+=j*tmp[i]*rem[i]%lcm;
				break;
			}
		}
	}
	ans%=lcm;
	printf("%lld",ans);
	return 0;
}