#include "bits/stdc++.h" using namespace std; using Graph = vector>; typedef long long ll; typedef pair P; #define rep(i,n) for (ll i = 0; i < (n); ++i) #define all(x) (x).begin(), (x).end() #define rall(x) (x).rbegin(), (x).rend() const long long mod = 1e9 + 7; ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; } ll lcm(ll a, ll b) { return a / gcd(a, b) * b; } int main() { ll n; cin >> n; ll ans=0; rep(i, n) { ll c, d; cin >> c >> d; c = (c + 1) / 2 % mod; d %= mod; ans += c*d; ans %= mod; } cout << ans << endl; }