
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] sumup = new int[n + 1];
		int[] sumdown = new int[n + 1];
		sumup[0] = 0;
		sumdown[0] = 0;
		for(int i = 1; i < n + 1; i++) {
			sumup[i] = sc.nextInt() + sumup[i - 1];
		}
		for(int i = 1; i < n + 1; i++) {
			sumdown[i] = sc.nextInt() + sumdown[i - 1];
		}
		int ans = 0;
		for(int i = 1; i < n + 1; i++) {
			int tmp = sumup[i] + sumdown[n] - sumdown[i - 1];
			ans = Math.max(ans, tmp);
		}
		System.out.println(ans);
	}

} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] sumup = new int[n + 1];
		int[] sumdown = new int[n + 1];
		sumup[0] = 0;
		sumdown[0] = 0;
		for(int i = 1; i < n + 1; i++) {
			sumup[i] = sc.nextInt() + sumup[i - 1];
		}
		for(int i = 1; i < n + 1; i++) {
			sumdown[i] = sc.nextInt() + sumdown[i - 1];
		}
		int ans = 0;
		for(int i = 1; i < n + 1; i++) {
			int tmp = sumup[i] + sumdown[n] - sumdown[i - 1];
			ans = Math.max(ans, tmp);
		}
		System.out.println(ans);
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] sumup = new int[n + 1];
		int[] sumdown = new int[n + 1];
		sumup[0] = 0;
		sumdown[0] = 0;
		for(int i = 1; i < n + 1; i++) {
			sumup[i] = sc.nextInt() + sumup[i - 1];
		}
		for(int i = 1; i < n + 1; i++) {
			sumdown[i] = sc.nextInt() + sumdown[i - 1];
		}
		int ans = 0;
		for(int i = 1; i < n + 1; i++) {
			int tmp = sumup[i] + sumdown[n] - sumdown[i - 1];
			ans = Math.max(ans, tmp);
		}
		System.out.println(ans);
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] sumup = new int[n + 1];
		int[] sumdown = new int[n + 1];
		sumup[0] = 0;
		sumdown[0] = 0;
		for(int i = 1; i < n + 1; i++) {
			sumup[i] = sc.nextInt() + sumup[i - 1];
		}
		for(int i = 1; i < n + 1; i++) {
			sumdown[i] = sc.nextInt() + sumdown[i - 1];
		}
		int ans = 0;
		for(int i = 1; i < n + 1; i++) {
			int tmp = sumup[i] + sumdown[n] - sumdown[i - 1];
			ans = Math.max(ans, tmp);
		}
		System.out.println(ans);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] sumup = new int[n + 1]; sumup new int[n + 1] n + 1 n 1 int[] sumdown = new int[n + 1]; sumdown new int[n + 1] n + 1 n 1 sumup[0] = 0 sumup[0] sumup 0 0 sumdown[0] = 0 sumdown[0] sumdown 0 0 for(int i = 1; i < n + 1; i++) {
			sumup[i] = sc.nextInt() + sumup[i - 1];
		} int i = 1; int i = 1; i 1 i < n + 1 i n + 1 n 1 i++ i++ i {
			sumup[i] = sc.nextInt() + sumup[i - 1];
		} {
			sumup[i] = sc.nextInt() + sumup[i - 1];
		} sumup[i] = sc.nextInt() + sumup[i - 1] sumup[i] sumup i sc.nextInt() + sumup[i - 1] sc.nextInt() sc.nextInt sc sumup[i - 1] sumup i - 1 i 1 for(int i = 1; i < n + 1; i++) {
			sumdown[i] = sc.nextInt() + sumdown[i - 1];
		} int i = 1; int i = 1; i 1 i < n + 1 i n + 1 n 1 i++ i++ i {
			sumdown[i] = sc.nextInt() + sumdown[i - 1];
		} {
			sumdown[i] = sc.nextInt() + sumdown[i - 1];
		} sumdown[i] = sc.nextInt() + sumdown[i - 1] sumdown[i] sumdown i sc.nextInt() + sumdown[i - 1] sc.nextInt() sc.nextInt sc sumdown[i - 1] sumdown i - 1 i 1 int ans = 0; ans 0 for(int i = 1; i < n + 1; i++) {
			int tmp = sumup[i] + sumdown[n] - sumdown[i - 1];
			ans = Math.max(ans, tmp);
		} int i = 1; int i = 1; i 1 i < n + 1 i n + 1 n 1 i++ i++ i {
			int tmp = sumup[i] + sumdown[n] - sumdown[i - 1];
			ans = Math.max(ans, tmp);
		} {
			int tmp = sumup[i] + sumdown[n] - sumdown[i - 1];
			ans = Math.max(ans, tmp);
		} int tmp = sumup[i] + sumdown[n] - sumdown[i - 1]; tmp sumup[i] + sumdown[n] - sumdown[i - 1] sumup[i] + sumdown[n] sumup[i] sumup i sumdown[n] sumdown n sumdown[i - 1] sumdown i - 1 i 1 ans = Math.max(ans, tmp) ans Math.max(ans, tmp) Math.max Math ans tmp System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] sumup = new int[n + 1];
		int[] sumdown = new int[n + 1];
		sumup[0] = 0;
		sumdown[0] = 0;
		for(int i = 1; i < n + 1; i++) {
			sumup[i] = sc.nextInt() + sumup[i - 1];
		}
		for(int i = 1; i < n + 1; i++) {
			sumdown[i] = sc.nextInt() + sumdown[i - 1];
		}
		int ans = 0;
		for(int i = 1; i < n + 1; i++) {
			int tmp = sumup[i] + sumdown[n] - sumdown[i - 1];
			ans = Math.max(ans, tmp);
		}
		System.out.println(ans);
	}

} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] sumup = new int[n + 1];
		int[] sumdown = new int[n + 1];
		sumup[0] = 0;
		sumdown[0] = 0;
		for(int i = 1; i < n + 1; i++) {
			sumup[i] = sc.nextInt() + sumup[i - 1];
		}
		for(int i = 1; i < n + 1; i++) {
			sumdown[i] = sc.nextInt() + sumdown[i - 1];
		}
		int ans = 0;
		for(int i = 1; i < n + 1; i++) {
			int tmp = sumup[i] + sumdown[n] - sumdown[i - 1];
			ans = Math.max(ans, tmp);
		}
		System.out.println(ans);
	}

} Main

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] sumup = new int[n + 1];
		int[] sumdown = new int[n + 1];
		sumup[0] = 0;
		sumdown[0] = 0;
		for(int i = 1; i < n + 1; i++) {
			sumup[i] = sc.nextInt() + sumup[i - 1];
		}
		for(int i = 1; i < n + 1; i++) {
			sumdown[i] = sc.nextInt() + sumdown[i - 1];
		}
		int ans = 0;
		for(int i = 1; i < n + 1; i++) {
			int tmp = sumup[i] + sumdown[n] - sumdown[i - 1];
			ans = Math.max(ans, tmp);
		}
		System.out.println(ans);
	}

}
