#include<bits/stdc++.h>
using namespace std;
typedef long long ll;

const ll mod=1000000007;

int main(){
    ll N;
    cin>>N;
    ll ans=0;
    while(N--){
        ll a,b;
        cin>>a>>b;
        a=(a+1)/2;
        a%=mod;
        b%=mod;
        ans+=(a*b)%mod;
        ans%=mod;
    }
    printf("%lld\n",ans);

    return 0;
}