import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int matrix[][] = new int[2][n];
		for(int i=0; i<2; i++) {
			for(int j=0; j<n; j++) {
				matrix[i][j] = scan.nextInt();
			}
		}
		scan.close();
		int cur, ans = 0;
		
		for(int i=0; i<n; i++) {
			cur = 0;
			for(int j=0, k=0; j<n; j++) {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			}
			if(cur > ans) ans = cur;
		}
		
		System.out.println(ans);
	}

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

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int matrix[][] = new int[2][n];
		for(int i=0; i<2; i++) {
			for(int j=0; j<n; j++) {
				matrix[i][j] = scan.nextInt();
			}
		}
		scan.close();
		int cur, ans = 0;
		
		for(int i=0; i<n; i++) {
			cur = 0;
			for(int j=0, k=0; j<n; j++) {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			}
			if(cur > ans) ans = cur;
		}
		
		System.out.println(ans);
	}

} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int matrix[][] = new int[2][n];
		for(int i=0; i<2; i++) {
			for(int j=0; j<n; j++) {
				matrix[i][j] = scan.nextInt();
			}
		}
		scan.close();
		int cur, ans = 0;
		
		for(int i=0; i<n; i++) {
			cur = 0;
			for(int j=0, k=0; j<n; j++) {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			}
			if(cur > ans) ans = cur;
		}
		
		System.out.println(ans);
	} main {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int matrix[][] = new int[2][n];
		for(int i=0; i<2; i++) {
			for(int j=0; j<n; j++) {
				matrix[i][j] = scan.nextInt();
			}
		}
		scan.close();
		int cur, ans = 0;
		
		for(int i=0; i<n; i++) {
			cur = 0;
			for(int j=0, k=0; j<n; j++) {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			}
			if(cur > ans) ans = cur;
		}
		
		System.out.println(ans);
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan int matrix[][] = new int[2][n]; matrix new int[2][n] 2 n for(int i=0; i<2; i++) {
			for(int j=0; j<n; j++) {
				matrix[i][j] = scan.nextInt();
			}
		} int i=0; int i=0; i 0 i<2 i 2 i++ i++ i {
			for(int j=0; j<n; j++) {
				matrix[i][j] = scan.nextInt();
			}
		} {
			for(int j=0; j<n; j++) {
				matrix[i][j] = scan.nextInt();
			}
		} for(int j=0; j<n; j++) {
				matrix[i][j] = scan.nextInt();
			} int j=0; int j=0; j 0 j<n j n j++ j++ j {
				matrix[i][j] = scan.nextInt();
			} {
				matrix[i][j] = scan.nextInt();
			} matrix[i][j] = scan.nextInt() matrix[i][j] matrix[i] matrix i j scan.nextInt() scan.nextInt scan scan.close() scan.close scan int cur cur ans = 0; ans 0 for(int i=0; i<n; i++) {
			cur = 0;
			for(int j=0, k=0; j<n; j++) {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			}
			if(cur > ans) ans = cur;
		} int i=0; int i=0; i 0 i<n i n i++ i++ i {
			cur = 0;
			for(int j=0, k=0; j<n; j++) {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			}
			if(cur > ans) ans = cur;
		} {
			cur = 0;
			for(int j=0, k=0; j<n; j++) {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			}
			if(cur > ans) ans = cur;
		} cur = 0 cur 0 for(int j=0, k=0; j<n; j++) {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			} int j=0, k=0; int j=0 j 0 k=0; k 0 j<n j n j++ j++ j {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			} {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			} cur += matrix[k][j] cur matrix[k][j] matrix[k] matrix k j if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				} j == n-(i+1) j n-(i+1) n (i+1) i 1 {
					k++;
					cur += matrix[k][j];
				} k++ k cur += matrix[k][j] cur matrix[k][j] matrix[k] matrix k j if(cur > ans) ans = cur; cur > ans cur ans ans = cur ans cur 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 scan = new Scanner(System.in);
		int n = scan.nextInt();
		int matrix[][] = new int[2][n];
		for(int i=0; i<2; i++) {
			for(int j=0; j<n; j++) {
				matrix[i][j] = scan.nextInt();
			}
		}
		scan.close();
		int cur, ans = 0;
		
		for(int i=0; i<n; i++) {
			cur = 0;
			for(int j=0, k=0; j<n; j++) {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			}
			if(cur > ans) ans = cur;
		}
		
		System.out.println(ans);
	}

} public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int matrix[][] = new int[2][n];
		for(int i=0; i<2; i++) {
			for(int j=0; j<n; j++) {
				matrix[i][j] = scan.nextInt();
			}
		}
		scan.close();
		int cur, ans = 0;
		
		for(int i=0; i<n; i++) {
			cur = 0;
			for(int j=0, k=0; j<n; j++) {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			}
			if(cur > ans) ans = cur;
		}
		
		System.out.println(ans);
	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int matrix[][] = new int[2][n];
		for(int i=0; i<2; i++) {
			for(int j=0; j<n; j++) {
				matrix[i][j] = scan.nextInt();
			}
		}
		scan.close();
		int cur, ans = 0;
		
		for(int i=0; i<n; i++) {
			cur = 0;
			for(int j=0, k=0; j<n; j++) {
				cur += matrix[k][j];
				if(j == n-(i+1)) {
					k++;
					cur += matrix[k][j];
				}
			}
			if(cur > ans) ans = cur;
		}
		
		System.out.println(ans);
	}

}