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

void main()
{
    int[1000] lane;
    immutable n = readln.chomp.to!int;
    readln.splitter.map!(to!int).copy(lane[]);
    foreach (i; 2..n) {
        lane[i] += lane[0..(i - 1)].reduce!max;
    }
    writeln(lane[0..n].reduce!max);
}