int N, a[100010];
char f[1000010];
int l = 0;
{
    rd(N, a(N));
    int ma = 0;
    REP(i, N){
        f[a[i]]++;
        while (f[a[i]] > 1)
            f[a[l++]]--;
        ma = max(ma, i-l+1);
    }
    wt(ma);
}