#include <bits/stdc++.h>

using namespace std;

const auto MOD = (long long) 1e9 + 7;

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