#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

const int MOD = 1000000007;

int main()
{
    int n;
    cin >> n;

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

    return 0;
}