HW1B

#include <iostream>
#include <vector>
#include <limits.h>

using namespace std;

int main()
{
    int MAX_SUM = 1000000000;
    int N;
    cin >> N;

    vector <int> a(N);
    for (int i = 0; i < N; i++) cin >> a[i];

    bool odd_place = true;
    int an = 0, b;
    long long sum = 0;
    for (int i = 0; i < N; i++) {
        cin >> b;

        while (b >= a[an]) {
            if (an != N) {
                if (odd_place) { sum = (sum + a[an]) % MAX_SUM; odd_place = false; }
                else if (odd_place) { odd_place = false; }
                else odd_place = true;
                an++;
                //cout << endl << "odd_place = " << odd_place << "; an = " << a[an - 1] << "; sum = " << sum << endl;
            }
            else break;
        }

        if (odd_place) { sum = (sum + b) % MAX_SUM; odd_place = false; }
        else odd_place = true;

        //cout << endl << "odd_place = " << odd_place << "; sum = " << sum << endl;
    }

    while (an < N) {
        if (odd_place) { sum = (sum + a[an]) % MAX_SUM; odd_place = false; }
        else odd_place = true;
        an++;
        //cout << endl << "odd_place = " << odd_place << "; an = " << a[an - 1] << "; sum = " << sum << endl;
    }

    cout << sum << endl;
}