#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

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