#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<cmath>
#include<cstdio>
using namespace std;
int main(){
    long long int N,sum=0,c,d,e;
    cin >> N;
    while(N--){
        cin >> c >> d;
        e = ((c+1)/2)%1000000007;
        sum += e;
        sum = sum % 1000000007;
    }
    cout << sum%1000000007;
    return 0;
}