import std.stdio, std.string, std.conv;
import std.range, std.algorithm, std.array;

void main() {
    int n;
    int[] a;

    scan(n);
    a = readln.split.to!(int[]);

    auto b = new bool[](a.reduce!max + 1);
    int ans;

    for (int l,r; r < n; r++) {
        if (b[a[r]]) {
            for (; b[a[r]]; l++) {
                b[a[l]] = 0;
            }
        }

        debug {
            writefln("(l, r) = (%s, %s)", l, r);
        }

        ans = max(ans, r - l + 1);
        b[a[r]] = 1;
    }

    writeln(ans);
}



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);
        }
    }
}