#include <bits/stdc++.h>

using namespace std;

#define LL long long
#define REP(i, n) for(int i = 0; i < n; i++)
const LL MOD = 1e9 + 7;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    LL n;
    cin >> n;
    LL ans = 0;
    REP(i, n) {
        LL c, d;
        cin >> c >> d;
        LL cc = ((c + 1) / 2) % MOD, dd = d % MOD;
        ans += (cc * dd) % MOD;
    }
    cout << (ans % MOD) << endl;
    return 0;
}