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

// dfmt off
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;}}
alias sread = () => readln.chomp();enum MOD = 10 ^^ 9 + 7;
alias PQueue = BinaryHeap!(Array!long, "a<b");
// dfmt on

void main()
{
    long N = lread();
    auto S = sread();
    long ans;
    long f;
    long b;
    outer: while (true)
    {
        if (f == b)
        {
            if (b < N)
            {
                b++;
                continue outer;
            }
            else
            {
                break outer;
            }
        }
        if (N <= f)
            break outer;
        foreach (i; b .. N - (b - f) + 1)
            if (S[f .. b] == S[i .. i + (b - f)])
            {
                // writefln("%d %d %s", f, b, S[f .. b]);
                ans = ans.max(b - f);
                if (b < N)
                {
                    b++;
                    continue outer;
                }
                else
                {
                    break outer;
                }
            }
        f++;
    }
    writeln(ans);
}
