#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
typedef long long ll;
#define rep(i,n) for(int i=0;i<(n);i++)
const ll mod = 1e9 + 7;
int main(void){
	ll n; cin >> n;
	ll ans = 0;
	rep(i, n){
		ll c, d; cin >> c >> d;
		/*
		if(c % 2 == 0){
			tmp = 
			ans += (c / 2) % mod * (d % mod) % mod;
		}else{
			ans += (c / 2 + 1) % mod * (d % mod) % mod;
		}
		*/
		(ans += (c + 1) / 2 % mod * (d % mod) % mod) %= mod;
		// ans %= mod;
	}
	printf("%lld\n", ans);
	return 0;
}