#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const ll MOD = 1e9+7;

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

    ll ans = 0;

    while (n--) {
        ll c, d; cin >> c >> d;
        ans += (c + 1) / 2 % MOD;
        ans *= d % MOD;
    }

    cout << ans << endl;
}