#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll mod = 1e9 + 7;

int main() {
    int N;
    ll ans = 0;
    cin >> N;

    while (N--) {
        ll C, D;
        cin >> C >> D;
        (C += 1) /= 2;
        C %= mod;
        D %= mod;
        ans += (C * D) % mod;
        ans %= mod;
    }

    cout << ans << endl;
}