#include <iostream>

using namespace std;

int
main()
{
        int n, i, j, total, max;

        cin >> n;
        int up[n], down[n];
        max = 0;
        for (i = 0; i < n; i++) {
                cin >> up[i];
        }
        for (i = 0; i < n; i++) {
                cin >> down[i];
        }

        for (i = 0; i < n; i++) {
                total = 0;
                for (int ii = 0; ii <= i; ii++) {
                        total += up[ii];
                }
                for (int jj = i; jj < n; jj++) {
                        total += down[jj];
                }
                if (total > max) {
                        max = total;
                }
        }

        cout << max << endl;
}