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

string FMT_F = "%.15f";

static string[] s_rd;
T RD(T = long)() { while(!s_rd.length) s_rd = readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
string RDR()() { return readln.chomp; }
T[] ARR(T = long)(in string str, T fix = 0) { auto r = str.split.to!(T[]); r[] += fix; return r; }
T[] RDA(T = long)(T fix = 0) { auto r = readln.chomp.split.to!(T[]); r[] += fix; return r; }
T[][] RDA2(T = long)(size_t n, T[] fix = []) { auto r = new T[][](n); foreach (i; 0..n) { r[i] = readln.chomp.split.to!(T[]); foreach (j, e; fix) r[i][j] += e; } return r; }
size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;}
size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; }

bool inside(T)(T x, T b, T e) { return x >= b && x < e; }
long lcm(long x, long y) { return x * y / gcd(x, y); }

long mod = 10^^9 + 7;
//long mod = 998244353;
//long mod = 1_000_003;
void moda(ref long x, long y) { x = (x + y) % mod; }
void mods(ref long x, long y) { x = ((x + mod) - (y % mod)) % mod; }
void modm(ref long x, long y) { x = (x * y) % mod; }

int binarySearch(alias pred, T)(in T[] arr, bool isLower = true)
{ 
	int ok, ng;
	if (isLower) { ok = cast(int)arr.length; ng = -1; }
	else		 { ok = -1; ng = cast(int)arr.length; }
	while (abs(ok-ng) > 1)
	{
		auto mid = (ok+ng) / 2;
		if (unaryFun!pred(arr[mid]))
			ok = mid;
		else ng = mid;
	}
	return ok;
}

void main()
{
	auto N = RD;
	auto S = RD!string;

	auto pos = new long[][](26);
	foreach (i; 0..N)
	{
		auto num = S[i] - 'a';
		pos[num] ~= i;
	}

	long ans;
	foreach (i; 0..N-1)
	{
		auto num = S[i] - 'a';
		auto pi = pos[num].binarySearch!((long a) => a > i)();
		foreach (j; pos[num][pi..$])
		{
			auto len1 = j - i;
			auto len2 = N - j;
			auto len = min(len1, len2);
			if (len <= ans) continue;
          	bool ok = true;
			foreach (k; 0..ans)
			{
				if (S[i+k] != S[j+k])
                {
                  ok = false;
                  break;
                }
			}
         	if (!ok) continue;
          	foreach (k; ans..len)
			{
				if (S[i+k] != S[j+k]) break;
				ans = max(ans, k+1);
			}
		}
	}

	writeln(ans);
	stdout.flush();
	debug readln();
}
