#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <algorithm>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <stack>
#include <queue>
#include <utility>
#define rep(i,l,n) for(lint i=l;i<n;i++)
#define rer(i,l,n) for(lint i=l;i<=n;i++)
#define all(a) a.begin(),a.end()
#define o(a) cout<<a<<endl
using namespace std;
typedef long long lint;
typedef vector<int> vi;
typedef vector<lint> vli;
typedef vector<vi> vvi;
typedef pair<int,int> pii;

lint mod=1e9+7;

int main(){
	lint n,c,d,ans=0;
	cin>>n;
	rep(i,0,n){
		cin>>c>>d;
		ans+=(c+1)/2*d;
		ans%=mod;
	}
	o(ans);
}