#include <iostream>
#include <vector>
#include <algorithm>
#include <string>

#define REP(i, a, b) for (int i = int(a); i < int(b); i++)
#define dump(val) cerr << __LINE__ << ":\t" << #val << " = " << (val) << endl

using namespace std;

typedef long long int lli;

const int mod = 1000000007;

int main() {
    int N;
    cin >> N;
    lli ans = 0;
    REP (i, 0, N) {
        lli C, D;
        cin >> C >> D;
        C = (C + 1) / 2;
        C %= mod;
        D %= mod;
        ans = (ans + (D * C) % mod) % mod;
    }
    cout << ans << endl;
    return 0;
}