#include<iostream>
#include<string>
#include<string.h>
#include<algorithm>
#include<stdio.h>
#include<cmath>
#include<vector>
#include<utility>
#include<stack>
#include<queue>
#include<list>
#include<bitset>
#include<functional>

#define FOR(i, a, b) for(int i=(a);i<=(b);i++)
#define RFOR(i, a, b) for(int i=(a);i>=(b);i--)
#define MOD 1000000007
#define INF 1000000000

using namespace std;
typedef pair<int, int> P;

int main(void) {
	int n;
	long long int total = 0;
	int c, d;

	cin >> n;
	FOR(i, 1, n) {
		cin >> c >> d;
		total += ((c + 1) / 2)*d;
		total %= MOD;
	}

	cout << total << endl;
	return 0;
}