import std.algorithm;
import std.range;
import std.stdio;
import std.math;
import std.array;
import std.string;
import std.conv;

/// 数列の読み込み
auto readNums(T = int)() {
	return readln().chomp.split.map!(to!T).array;
}

/// 数の読み込み
auto readNum(T = int)() {
	return readNums!T.front;
}

/// 指定行数読み込み
auto readRows(size_t rows) {
	return generate(() => readln().chomp).take(rows).array;
}

void main() {
    immutable n = readNum();
    const row1 = readNums();
    const row2 = readNums();
    int candies = 0;
    foreach(i; 0 .. n) {
        candies = max(candies, row1[0 .. i + 1].sum + row2[i .. $].sum);
    }
    writeln(candies);
}