#include <cstdio>
#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <cstring>
#include <sstream>
#include <algorithm>
#include <functional>
#include <queue>
#include <stack>
#include <cmath>
#include <list>
#include <iomanip>
#include <fstream>

using namespace std;
inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v; }
template<class T> inline string toString(T x) { ostringstream sout; sout << x; return sout.str(); }
template<class T> inline T sqr(T x) { return x*x; }
typedef pair<int, int> P;
typedef long long ll;
typedef unsigned long long ull;

#define rep(i,n)  for(int (i) = 0;(i) < (n);(i)++)
#define clr(a) memset((a), 0 ,sizeof(a))
#define mclr(a) memset((a), -1 ,sizeof(a))
#define all(a)  (a).begin(),(a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define sz(a) (sizeof(a))
#define Fill(a,v) fill((int*)a,(int*)(a+(sz(a)/sz(*(a)))),v)
bool cheak(int x, int y, int xMax, int yMax){ return x >= 0 && y >= 0 && xMax > x && yMax > y; }
const int dx[4] = { -1, 0, 1, 0 }, dy[4] = { 0, 1, 0, -1 };
const int mod = 1000000007;
const int INF = 2147483647;

int main()
{
	int n;
	cin >> n;
	int ans = 0;
	rep(i, n){
		ull c,d;
		cin >> c >> d;
		ans += (((c+1)/2) % mod) * (d % mod) % mod;
	}
	cout << ans << endl;
}