#include <iostream>
#include <vector>

using namespace std;

int main() {
    int n;
    cin >> n;
    long long ans = 0;
    long long mod = 1e9 + 7;
    for (int i = 0; i < n; ++i) {
        long long c, d;
        cin >> c >> d;
        ans += ((((c + 1) / 2) % mod) * (d % mod)) % mod;
    }
    cout << (ans % mod) << endl;
    return 0;
}