#include <cstdio>
#include <algorithm>
#define maxn 5001

FILE *in = fopen("secv.in","r"), *out = fopen("secv.out","w");

int n;
int a[maxn];
int b[maxn];
int c[maxn];
int l[maxn][maxn];

void read()
{
    fscanf(in, "%d", &n);

    for ( int i = 1; i <= n; ++i )
        fscanf(in, "%d", &a[i]), b[i] = a[i];


}

int main()
{
    read();
    std::sort(b+1, b+n);

    int k = 0;
    c[++k] = b[1];
    for ( int i = 2; i <= n; ++i )
        if ( b[i] != c[k] )
            c[++k] = b[i];

    for ( int i = 1; i <= n; ++i )
        for ( int j = 1; j <= k; ++j )
        {
            if ( a[i] == c[j] )
                l[i][j] = l[i-1][j-1] + 1;
            else
            {
                if ( l[i-1][j] > l[i][j-1] )
                    l[i][j] = l[i-1][j] + 1;
                else
                    l[i][j] = l[i][j-1] + 1;
            }
        }


//    for ( int i = 1; i <= n; ++i )
//    {
//        for ( int j = 1; j <= k; ++j )
//            printf("%d ", l[i][j]);
//        printf("\n");
//    }

    fprintf(out, "%d\n", l[n][k]);


	return 0;
}

/*

8
2 1 3 2 1 3 4 5

1 2 3 4 5

*/