#include <iostream>
#include <algorithm>
using namespace std;
typedef long long LL;

const LL MOD=1000000007;

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