#include <bits/stdc++.h>
using namespace std;
int n, f[3][110], a[3][110];
int Read() {
  int x = 0, f = 1;
  char ch = getchar();
  while (!isdigit(ch)) {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = (x << 1) + (x << 3) + ch - '0';
    ch = getchar();
  }
  return f * x;
}
int main() {
  n = Read();
  for (int i = 1; i <= 2; i++)
    for (int j = 1; j <= n; j++) a[i][j] = Read();
  f[1][1] = a[1][1];
  for (int i = 1; i <= 2; i++)
    for (int j = 1; j <= n; j++) {
      if (i == 1)
        f[i][j] = f[i][j - 1] + a[i][j];
      else
        f[i][j] = max(f[i][j - 1], f[i - 1][j]) + a[i][j];
    }
  cout << f[2][n];
  return 0;
}
