#include<bits/stdc++.h>

using namespace std;

typedef long long LL;


void Gcd(LL a,LL b,LL &x,LL &y)
{
   if(!b)
   {
		x = 1, y = 0;
		return;
   }
   Gcd(b, a % b, y, x);
   y -= (a / b) * x;
}
LL CRT(LL k,LL* a,LL* b)
{
  LL p = 1, ans = 0;
  for (int i = 1;i <= k;i ++)
  {
	p = p * a[i];
  }
  for (int i = 1;i <= k;i++)
  {
    LL m = p / a[i], x, y;
    Gcd(m, a[i], x, y);
    ans = (ans + b[i] * m * x % p) % p;
  }
  return (ans % p + p) % p;
}

int n;
LL a[100010];
LL b[100010];

int main()
{
	scanf("%d",&n);
	for(int i = 1;i <= n;i ++)
	{
		scanf("%lld%lld",a + i,b + i);
	}
	printf("%lld",CRT(n,a,b));
	return 0;
}