#include <iostream>
using namespace std;

using ll = unsigned long long int;

ll Multiplation(ll a,ll b){
    if(b == 0){
        return 0;
    }
    ll tmp = 2*Multiplation(a,b>>1);
    tmp %= 1000000007;
    if(b%2 == 1){
        tmp += a;
        tmp %= 1000000007;
        return tmp;
    }else{
        return tmp;
    }
}


int main(void){
    // Here your code !
    int n;
    cin >> n;
    ll res = 0;
    
    for(int i = 0; i < n; i++){
        ll c,d;
        cin >> c >> d;
        
        c %= 1000000007;
        d %= 1000000007;
        
        c = (c+1)/2;
        
        res += c*d;
        
        res %= 1000000007;
    }
    
    cout << res << endl;
    
}