import std.stdio;
import std.algorithm;
import std.string;
import std.conv;

void main()
{
    int[1000] lane, tasteMemo;
    immutable n = readln.chomp.to!int;
    readln.splitter.map!(to!int).copy(lane[]);

    foreach (i, x; lane[0..n]) {
        if (i < 2) {
            tasteMemo[i] = x;
            continue;
        }
        int max = 0;
        foreach_reverse (j, y; tasteMemo[0..(i - 1)]) {
            if (y > max) {
                max = y;
            }
        }
        tasteMemo[i] = x + max;
    }
    writeln(tasteMemo.reduce!max);
}