#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <cstring>

typedef long long ll;
using namespace std;

#define mod 1000000007
#define INF 1000000000 //(int)1e9
#define LLINF 2000000000000000000 //(ll)2e18
#define PI  3.1415926536

#define SIZE 100000

int main(){
    int n;
    ll c,d;
    ll ans = 0;
    
    scanf("%d",&n);
    
    for(int i=0;i<n;i++){
        scanf("%lld%lld",&c,&d);
        
        ans += ((((c+1)/2)%mod) * (d%mod))%mod;
        ans %= mod;
        
    }
    
    printf("%lld\n",ans);
    
    return 0;
}