#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <utility>
#include <stack>
#include <functional>
#include <queue>
#include <cmath>
#include <set>
#include <map>

#define rep(i,j,k) for(int i=(int)j;i<(int)k;i++)
#define Sort(x) sort((x).begin(),(x).end())
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define vi vector<int>
#define INF (int)1e933
#define INFL 1e18
#define MOD 1000000007
#define pb push_back
#define MP make_pair
typedef long long ll;
typedef std::pair<int,int> pii;
int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};

using namespace std;
void mod(ll *a){
    if(*a>MOD)*a%=MOD;
}

int main() {
    int n; cin>>n;
    ll ans=0;
    rep(i,0,n){
        ll x,y;
        cin>>x>>y;
        mod(&x); mod(&y);
        
        if(x%2){
            ans+=y*(x/2+1);
        }else ans+=y*(x/2);
        mod(&ans);
    }
    cout<<ans<<endl;
    return 0;
}