#include <bits/stdc++.h>
using namespace std;
#define IO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
const long long N = 2e5 + 5, MOD = 1e9 + 7, OO = 1e18;
const double PI = acos(-1);
const int dx[4] = {0, 0, 1, -1};
const int dy[4] = {1, -1, 0, 0};

long long n, a[3][N], mem[N][3];

long long solve(long long idx, long long s) {
    if (idx == n + 1)return 0;
    long long &ret = mem[idx][s];
    if (!ret)return ret;
    long long c1 = -OO, c2 = -OO, c3 = -OO;
    if (s == 0 || s == 2)
        c1 = a[1][idx] + solve(idx + 1, 1LL);
    if (s == 0 || s == 1)
        c2 = a[2][idx] + solve(idx + 1, 2LL);
    c3 = solve(idx + 1, s);
    return ret = max({c1, c2, c3});
}

int main() {
    IO
    memset(mem, -1, sizeof mem);
    cin >> n;
    for (int i = 1; i <= 2; i++)
        for (int j = 1; j <= n; j++)cin >> a[i][j];
    cout << solve(1LL, 0LL);
    return 0;
}