#include <bits/stdc++.h>
#define LL long long
using namespace std;
int main (){
    
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    LL n;
    cin >> n;
    
    LL res{0};
    const LL mod = 1000000007;

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