#define _USE_MATH_DEFINES
#define _CRT_SECURE_NO_DEPRECATE

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <cfloat>
#include <ctime>
#include <cassert>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <numeric>
#include <list>
#include <iomanip>
#include <fstream>
#include <iterator>
#include <bitset>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> Pii;
typedef pair<ll, ll> Pll;

#define FOR(i,n) for(int i = 0; i < (n); i++)
#define sz(c) ((int)(c).size())
#define ten(x) ((int)1e##x)
#define tenll(x) ((ll)1e##x)
template<class T> T gcd(T a, T b) { return b ? gcd(b, a % b) : a; }

int main(){
	int n; cin >> n;
	const int MOD = ten(9) + 7;
	ll ans = 0;
	while (n--) {
		ll c, d; cin >> c >> d;
		ans += ((c + 1) / 2) % MOD * (d % MOD) % MOD;
	}
	cout << ans % MOD << endl;
}