#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD 1000000007
using namespace std;
typedef long long LL;
typedef vector<int> VI;

int main() {
	int n;
	cin >> n;
	LL ans = 0;
	REP(i, n) {
		LL c, d;
		cin >> c >> d;
		if (c % 2 == 0) ans += (c / 2) * d;
		else ans += (c / 2 + 1) * d;
	}
	cout << ans % MOD << endl;
	return 0;
}