#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <map>
#include <cmath>
#include <queue>
#include <numeric>
#include <climits>
#include <iterator>
#include <iomanip>
#include <stack>
#include <set>
#include <bitset>
#include <functional>
using namespace std;
const constexpr int INF = 1e9;
//typedef std::pair<std::string,double> P;


#define FOR(i, a, n) for (ll i = (ll)a; i<(ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)

typedef long long ll;
typedef vector<int> VI;
const constexpr ll MOD = 1e9+7;
vector<pair<int, int> > vp;
 
struct Less {
    bool operator()(const pair<int, int>& x, const pair<int, int>& y) const {
        return x.first > y.first;
    }
};

ll GCD(ll a, ll b){
    if(b==0) return a;
    return GCD(b, a%b);
}


//グラフの隣接リスト
VI g[200010];
//頂点の入次数を管理
int h[100010];
string s;
int a[100010];
int b[100010]={INF};
int main(void) {
    int N; cin >> N;
    
    ll ans =0;
    REP(i, N){
        ll C, D; cin >> C >> D;
        C = (C+1)/2%MOD; D=D%MOD;
        ans += (C*D)%MOD;
        ans = ans %MOD;
    }
    
    cout << ans << endl;
    
}