#include <bits/stdc++.h>
typedef long long ll;
#define INF 1000000000
#define MOD 1000000007
using namespace std;
int main(void){
    int n;
    cin>>n;
    ll ans=0;
    for(int i=0;i<n;i++){
        ll c,d;
        cin>>c>>d;
        c%=MOD;
        d%=MOD;
        ans+=(((c+1)/2)%MOD)*d%MOD;
        ans%=MOD;
    }
    cout<<ans<<endl;
}