#include <bits/stdc++.h>

#define pout(n)  printf ("%d\n", n)

#define rep(i,a,n) for (int i = a;i < n;i++)
#define per(i,a,n) for (int i = n-1;i >= a;i--)

const int d4x[4] = {1, 0, -1, 0};
const int d4y[4] = {0, 1, 0, -1};
const int d8x[8] = { 1,1,0,-1,-1,-1,0,1 };
const int d8y[8] = { 0,1,1,1,0,-1,-1,-1 };

#define MAX_N (int)2e5+20
#define INF 1e12+20

typedef long long ll;
using namespace std;

long mod = (int)1e9 + 7;
ll c,d,ans = 0;
int n;
int main() {
    cin >> n;
    rep(i,0,n){
        cin >> c >> d;
        c = (c+1)/2 % mod;
        d %= mod;
        ans += c*d;
        ans %= mod;
    }
    printf("%lld\n",ans);
    return 0;
}