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;
    foreach (f0; 0 .. N)
        foreach (f1; f0 + 1 .. N)
        {
            inner: foreach (len; 0 .. min(f1 - f0, N - f1))
                if (S[f0 + len] == S[f1 + len])
                {
                    // writefln("%d %d %d %s", f0, f1, len + 1, S[f0 .. f0 + len + 1]);
                    ans = ans.max(len + 1);
                }
                else
                {
                    break inner;
                }
        }
    writeln(ans);
}
