#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <stack>
#include <algorithm>
#include <string>
#include <map>
#include <iterator>
#include <set>
#include <queue>
#include <bitset>
#include <cassert>

using namespace std;


const int MOD = 1000000007;


int main() {

    int N;
    cin >> N;

    long long res = 0;
    for (int i = 0; i < N; ++i) {

        long long C, D;
        cin >> C >> D;

        
        res = ((res % MOD) + (((C + 1) / 2) % MOD * (D % MOD)) % MOD) % MOD;
    }

    cout << res << endl;

    return 0;

}