#include <vector>
#include <string>
#include <algorithm>
#include <numeric>
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <utility>
#include <list>
#include <queue>
#include <map>
#include <iterator>
#include <iomanip>
#include <complex>
using namespace std;

using ull = unsigned long long;
using ll = long long;

ull Mod = 1e9 + 7;

int main()
{
    ull n;
    cin >> n;

    ull sum = 0;
    for(int i =0; i < n; ++i)
    {
        ull c,d;
        cin >> c >> d;

        sum = (sum + ((c+1)/2)*d) % Mod;
    }

    cout << sum << endl;
}