#include <algorithm>
#include <array>
#include <cmath>
#include <cstdio>
#include <iostream>
#include <numeric>
#include <optional>
#include <vector>

using namespace std;

int main() {
    int32_t n;
    cin >> n;
    const uint64_t mod = 1000 * 1000 * 1000 + 7;
    uint64_t ans = 0;
    for (auto i = 0; i < n; ++i) {
        uint64_t c, d;
        cin >> c >> d;
        uint64_t t = (c + 1) / 2 % mod;
        t = d % mod * t % mod;
        ans = (ans + t) % mod;
    }
    cout << ans << endl;
    return 0;
}