UVALive 4764 dp

#include<stdio.h>
#include<string.h>
#include<iostream>
using namespace std;
#define N 100000+10

int vis[N];
int num[N];
int dp[N];

int main()
{
    int n;
    while(cin >> n)
    {
        if (n == 0) break;
        memset(vis, 0, sizeof(vis));
        memset(num, 0, sizeof(num));
        memset(dp, 0, sizeof(dp));

        for (int i=0; i<n; ++i)
        {
            cin >> num[i];
        }
        int pre = num[0];
        int nnext;
        vis[pre] = 1;

        int ans = 0;

        for (int i=1; i<n; ++i)
        {
            nnext = num[i];
            if (!vis[nnext])
            {
                vis[nnext] = 1;
                dp[nnext] = dp[pre];
            }

            else
            {
                if (nnext == 999)
                {
                    dp[nnext] = max(dp[pre], dp[nnext]+3);
                }
                else
                {
                    dp[nnext] = max(dp[pre], dp[nnext]+1);
                }
            }
            pre = nnext;
            if (ans < dp[nnext])
                ans = dp[nnext];
        }
        cout << ans << endl;
    }
    return 0;
}