import std.stdio;
import std.algorithm;
import std.string : chomp;
import std.range;
import std.conv;

void main(string[] args)
{
    immutable n = readln.chomp.to!int;
    readln
        .splitter
        .map!(to!int)
        .map!(x => iota(x, n + 1, x))
        .join
        .sort()
        .uniq
        .walkLength
        .writeln;
}