#include <iostream>
#include <string>
#include <vector>
using namespace std;

int main(){
	const long long mod = 1e9 + 7;
	int a;
	cin >> a;
	long long b,c;
	long long sum=0;
	for(int i=0; i<a; i++){
		cin >> b >> c;
		if(b%2==0)  sum += (b/2)%mod * (c%mod)%mod;
		else  sum += (b/2+1)%mod * (c%mod)%mod;
		sum %= mod;
	}
	cout << sum << endl;
	return 0;
}