#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)s; i < (int)e; i++)

ll mod = 1e9 + 7;

int main() {
    cin.tie(nullptr);
    
    int N;
    cin >> N;
    
    ll ans = 0;
    
    rep(i, 0, N) {
        ll C, D;
        cin >> C >> D;
        
        D %= mod;
        
        ans += ((C + 1) / 2) % mod * D;
        ans %= mod;
    }
    
    cout << ans << '\n';
}