#include <iostream>
#include <vector>
#include <string>
#include <cmath>
#include <iomanip>
#include <algorithm>
using namespace std;
using ll = long long;
constexpr ll M = 1e9+7;

int main() {
    ll N;
    cin >> N;
    ll res = 0;
    for(int i=0; i<N; ++i) {
        ll c, d;
        cin >> c >> d;
        d %= M;
        res += (((c+1)/2) % M) * d;
        res %= M;
    }
    cout << res << endl;
}