#define sz(s) (int)(s).size()
#define all(s) (s).begin(),(s).end()

vector<int> v;
int n;
const int N = 1e4;
int dp[N][301];
int vis[N][301], vid = 0;
static int nxt[10005][301];
inline int get_next(int i, int val) {
    if (val<1 || val>300 || i+1>n) return -1;
    return nxt[i+1][val];
}
int rec(int i, int diff) {
    if (i == n || diff==-1)return 0;
    int &ret = dp[i][diff];
    if (vis[i][diff] == vid)return ret;
    vis[i][diff] = vid;
    ret = 0;
    if (diff == 300)ret = max(ret, rec(i + 1, diff));
    ret=max(ret,rec(i,diff-1));
    int next1 = get_next(i, v[i] + diff);
    int next2 = get_next(i, v[i] - diff);
    if (next1 != -1) ret = max(ret, rec(next1, diff) + 1);
    if (next2 != -1 && next2 != next1) ret = max(ret, rec(next2, diff) + 1);

    return ret;
}

class Solution {
public:
     static int longestSubsequence(vector<int> &nums) {
        vid++;
        v = nums;
        n = sz(nums);
        for (int v=1; v<=300; ++v) nxt[n][v] = -1;
     for (int i=n-1; i>=0; --i) {
    memcpy(nxt[i], nxt[i+1], 301*sizeof(int));
    nxt[i][nums[i]] = i;
    }
        return rec(0,300)+1;
    }
};