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

enum inf = 1_001_001_001;
enum inf6 = 1_001_001_001_001_001_001L;
enum mod = 1_000_000_007L;


void main() {
    int N;
    string S;
    scan(N);
    scan(S);

    int ans;

    foreach (l ; 0 .. N) {
        auto z = Zalg(S[l .. $]);
        debug {
            writeln(z);
        }
        foreach (j ; 0 .. N - l) {
            ans = max(ans, min(j, z[j]));
        }
    }

    writeln(ans);
}

int[] Zalg(string S) {
    int N = S.length.to!int;
    auto z = new int[](N);
    z[0] = N;

    for (int i = 1, j = 0; i < N; ) {
        while (i + j < N && S[j] == S[i + j]) j++;
        z[i] = j;

        if (j == 0) {
            i++;
            continue;
        }

        int k = 1;
        while (i + k < N && k + z[k] < j) {
            z[i + k] = z[k];
            k++;
        }
        i += k;
        j -= k;
    }

    return z;
}






void scan(T...)(ref T args) {
    import std.stdio : readln;
    import std.algorithm : splitter;
    import std.conv : to;
    import std.range.primitives;

    auto line = readln().splitter();
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront();
    }
    assert(line.empty);
}

void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}

bool chmin(T, U...)(ref T x, U args) {
    bool isChanged;

    foreach (arg; args) {
        if (x > arg) {
            x = arg;
            isChanged = true;
        }
    }

    return isChanged;
}

bool chmax(T, U...)(ref T x, U args) {
    bool isChanged;

    foreach (arg; args) {
        if (x < arg) {
            x = arg;
            isChanged = true;
        }
    }

    return isChanged;
}
