#include <bits/stdc++.h>
#define LL long long
#define ULL unsigned long long
#define REP(i,n) for(int i=0; i<(n); i++)
#define REP2(i,x,n) for(int i=x; i<(n); i++)
using namespace std;
int main (){
    
    cin.tie(0);
    ios::sync_with_stdio(false);
	
    LL n;
    cin >> n;
    
    LL c, d, res{0};
	const LL mod = 1000000007;

    for( LL i = 0; i < n; i++ ){
		
        cin >> c >> d;
        
		if( ( c % 2 ) % mod  != 0 ){
            c += 1;
        }
        res += ( ( c / 2 ) * d ) % mod;
    }
    cout << res << endl;
	
    return 0;
}