import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] A1 = new int[N + 1];
		int[] A2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			A1[i] = sc.nextInt();
		}
		for (int i = 1; i <= N; i++) {
			A2[i] = sc.nextInt();
		}
		int[] s1 = new int[N + 1];
		int[] s2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			int j = N - i + 1;
			if (i == 1) {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} else {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			}
		}
		int max = 0;
		for (int i = 1; i <= N; i++) {
			if (i == 1 || max < s1[i] + s2[i]) {
				max = s1[i] + s2[i];
			}
		}
		System.out.println(max);
	}

} 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[] A1 = new int[N + 1];
		int[] A2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			A1[i] = sc.nextInt();
		}
		for (int i = 1; i <= N; i++) {
			A2[i] = sc.nextInt();
		}
		int[] s1 = new int[N + 1];
		int[] s2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			int j = N - i + 1;
			if (i == 1) {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} else {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			}
		}
		int max = 0;
		for (int i = 1; i <= N; i++) {
			if (i == 1 || max < s1[i] + s2[i]) {
				max = s1[i] + s2[i];
			}
		}
		System.out.println(max);
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] A1 = new int[N + 1];
		int[] A2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			A1[i] = sc.nextInt();
		}
		for (int i = 1; i <= N; i++) {
			A2[i] = sc.nextInt();
		}
		int[] s1 = new int[N + 1];
		int[] s2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			int j = N - i + 1;
			if (i == 1) {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} else {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			}
		}
		int max = 0;
		for (int i = 1; i <= N; i++) {
			if (i == 1 || max < s1[i] + s2[i]) {
				max = s1[i] + s2[i];
			}
		}
		System.out.println(max);
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] A1 = new int[N + 1];
		int[] A2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			A1[i] = sc.nextInt();
		}
		for (int i = 1; i <= N; i++) {
			A2[i] = sc.nextInt();
		}
		int[] s1 = new int[N + 1];
		int[] s2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			int j = N - i + 1;
			if (i == 1) {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} else {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			}
		}
		int max = 0;
		for (int i = 1; i <= N; i++) {
			if (i == 1 || max < s1[i] + s2[i]) {
				max = s1[i] + s2[i];
			}
		}
		System.out.println(max);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int[] A1 = new int[N + 1]; A1 new int[N + 1] N + 1 N 1 int[] A2 = new int[N + 1]; A2 new int[N + 1] N + 1 N 1 for (int i = 1; i <= N; i++) {
			A1[i] = sc.nextInt();
		} int i = 1; int i = 1; i 1 i <= N i N i++ i++ i {
			A1[i] = sc.nextInt();
		} {
			A1[i] = sc.nextInt();
		} A1[i] = sc.nextInt() A1[i] A1 i sc.nextInt() sc.nextInt sc for (int i = 1; i <= N; i++) {
			A2[i] = sc.nextInt();
		} int i = 1; int i = 1; i 1 i <= N i N i++ i++ i {
			A2[i] = sc.nextInt();
		} {
			A2[i] = sc.nextInt();
		} A2[i] = sc.nextInt() A2[i] A2 i sc.nextInt() sc.nextInt sc int[] s1 = new int[N + 1]; s1 new int[N + 1] N + 1 N 1 int[] s2 = new int[N + 1]; s2 new int[N + 1] N + 1 N 1 for (int i = 1; i <= N; i++) {
			int j = N - i + 1;
			if (i == 1) {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} else {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			}
		} int i = 1; int i = 1; i 1 i <= N i N i++ i++ i {
			int j = N - i + 1;
			if (i == 1) {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} else {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			}
		} {
			int j = N - i + 1;
			if (i == 1) {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} else {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			}
		} int j = N - i + 1; j N - i + 1 N - i N i 1 if (i == 1) {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} else {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			} i == 1 i 1 {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} s1[i] = A1[i] s1[i] s1 i A1[i] A1 i s2[j] = A2[j] s2[j] s2 j A2[j] A2 j {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			} s1[i] = A1[i] + s1[i - 1] s1[i] s1 i A1[i] + s1[i - 1] A1[i] A1 i s1[i - 1] s1 i - 1 i 1 s2[j] = A2[j] + s2[j + 1] s2[j] s2 j A2[j] + s2[j + 1] A2[j] A2 j s2[j + 1] s2 j + 1 j 1 int max = 0; max 0 for (int i = 1; i <= N; i++) {
			if (i == 1 || max < s1[i] + s2[i]) {
				max = s1[i] + s2[i];
			}
		} int i = 1; int i = 1; i 1 i <= N i N i++ i++ i {
			if (i == 1 || max < s1[i] + s2[i]) {
				max = s1[i] + s2[i];
			}
		} {
			if (i == 1 || max < s1[i] + s2[i]) {
				max = s1[i] + s2[i];
			}
		} if (i == 1 || max < s1[i] + s2[i]) {
				max = s1[i] + s2[i];
			} i == 1 || max < s1[i] + s2[i] i == 1 i 1 max < s1[i] + s2[i] max s1[i] + s2[i] s1[i] s1 i s2[i] s2 i {
				max = s1[i] + s2[i];
			} max = s1[i] + s2[i] max s1[i] + s2[i] s1[i] s1 i s2[i] s2 i System.out.println(max) System.out.println System.out System System.out max String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] A1 = new int[N + 1];
		int[] A2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			A1[i] = sc.nextInt();
		}
		for (int i = 1; i <= N; i++) {
			A2[i] = sc.nextInt();
		}
		int[] s1 = new int[N + 1];
		int[] s2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			int j = N - i + 1;
			if (i == 1) {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} else {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			}
		}
		int max = 0;
		for (int i = 1; i <= N; i++) {
			if (i == 1 || max < s1[i] + s2[i]) {
				max = s1[i] + s2[i];
			}
		}
		System.out.println(max);
	}

} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] A1 = new int[N + 1];
		int[] A2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			A1[i] = sc.nextInt();
		}
		for (int i = 1; i <= N; i++) {
			A2[i] = sc.nextInt();
		}
		int[] s1 = new int[N + 1];
		int[] s2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			int j = N - i + 1;
			if (i == 1) {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} else {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			}
		}
		int max = 0;
		for (int i = 1; i <= N; i++) {
			if (i == 1 || max < s1[i] + s2[i]) {
				max = s1[i] + s2[i];
			}
		}
		System.out.println(max);
	}

} 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[] A1 = new int[N + 1];
		int[] A2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			A1[i] = sc.nextInt();
		}
		for (int i = 1; i <= N; i++) {
			A2[i] = sc.nextInt();
		}
		int[] s1 = new int[N + 1];
		int[] s2 = new int[N + 1];
		for (int i = 1; i <= N; i++) {
			int j = N - i + 1;
			if (i == 1) {
				s1[i] = A1[i];
				s2[j] = A2[j];
			} else {
				s1[i] = A1[i] + s1[i - 1];
				s2[j] = A2[j] + s2[j + 1];
			}
		}
		int max = 0;
		for (int i = 1; i <= N; i++) {
			if (i == 1 || max < s1[i] + s2[i]) {
				max = s1[i] + s2[i];
			}
		}
		System.out.println(max);
	}

}
