import core.bitop;
import std.algorithm;
import std.ascii;
import std.bigint;
import std.conv;
import std.functional;
import std.math;
import std.numeric;
import std.range;
import std.stdio;
import std.string;
import std.random;
import std.typecons;
import std.container;

alias sread = () => readln.chomp();
ulong MOD = 1_000_000_007;
ulong INF = 1_000_000_000_000;
alias Grid = Tuple!(long, "x", long, "y");

T lread(T = long)()
{
    return readln.chomp.to!T();
}

T[] aryread(T = long)()
{
    return readln.split.to!(T[])();
}

void scan(TList...)(ref TList Args)
{
    auto line = readln.split();
    foreach (i, T; TList)
    {
        T val = line[i].to!(T);
        Args[i] = val;
    }
}

void main()
{
    auto n = lread();
    auto a = aryread();
    auto b = aryread();
    auto com_a = new long[](n);
    auto com_b = new long[](n + 1);
    com_a[0] = a[0], com_b[1] = b[0];
    foreach (i; iota(1, n))
    {
        com_a[i] += com_a[i - 1] + a[i];
        com_b[i + 1] += com_b[i] + b[i];
    }
    // com_a.writeln();
    // com_b.writeln();
    long moves;
    foreach(i; iota(n))
    {
        auto cost = com_a[i] + com_b[$ - 1] - com_b[i];
        moves = max(cost, moves);
    }
    moves.writeln();
}
