Go: package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"strconv"
)

const (
	initialBufSize = 10000000
	maxBufSize     = 100000000
)

var sc *bufio.Scanner

func initScanner(r io.Reader) *bufio.Scanner {
	buf := make([]byte, initialBufSize)

	sc := bufio.NewScanner(r)
	sc.Buffer(buf, maxBufSize)
	sc.Split(bufio.ScanWords) // bufio.ScanLines
	return sc
}

func main() {
	sc = initScanner(os.Stdin)
	resolve()
}

func nextInt(sc *bufio.Scanner) int {
	sc.Scan()
	a, _ := strconv.Atoi(sc.Text())
	return int(a)
}
func nextString(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

func nextIntSlice(sc *bufio.Scanner, n int) (a []int) {
	a = make([]int, n)
	for i := 0; i < n; i++ {
		a[i] = nextInt(sc)
	}
	return a
}

var dp [][]int

func initDP(n int) {
	dp = make([][]int, n+1)
	for i := 0; i < len(dp); i++ {
		dp[i] = make([]int, n+1)
		for j := 0; j < len(dp[0]); j++ {
			dp[i][j] = -1
		}
	}
}

func resolve() {
	ans := []int{}
	for true {
		n := nextInt(sc)
		if n == 0 {
			break
		}
		as := nextIntSlice(sc, n)
		initDP(n)
		_rec(as, n, 0, n)
		ans = append(ans, dp[0][n])
	}
	for _, v := range ans {
		fmt.Println(v)
	}
	return
}

func _rec(as []int, n, l, r int) int {
	if dp[l][r] > -1 {
		return dp[l][r]
	}
	if r-l == 1 { // prevent to hit daruma
		dp[l][r] = 0
		return dp[l][r]
	}
	if r-l == 2 {
		if abs(as[l]-as[r-1]) <= 1 {
			dp[l][r] = 2
		} else {
			dp[l][r] = 0
		}
		return dp[l][r]
	}
	if abs(as[l]-as[r-1]) <= 1 {
		v := _rec(as, n, l+1, r-1)
		// if we can remove internal blocks
		if (r - 1 - (l + 1)) == v {
			dp[l][r] = v + 2
			return dp[l][r]
		} else {
			dp[l][r] = v
		}
	}
	for i := l + 1; i < r; i++ {
		v := _rec(as, n, l, i) + _rec(as, n, i, r)
		if dp[l][r] < v {
			dp[l][r] = v
		}
	}
	return dp[l][r]
}

func abs(v int) int {
	if v < 0 {
		return -v
	}
	return v
}

C++: #include <iostream>
#include <ccomplex>
#include <vector>
#include <cassert>
#include <utility>
#include <algorithm>
#include <string>
#include <deque>
#include <queue>
#include <functional>
#include <cmath>
#include <iomanip>
#include <map>
#include <numeric>
#include <list>
#include <assert.h>
#include <math.h>
#include <valarray>
#include <stdio.h>
#include <algorithm>
#include <set>
#include <complex>
#include <list>
#include <time.h>
#include <stack>
#include <locale>
#include <clocale>
#include <ctype.h>
#include <wchar.h>

using namespace std;
typedef long long int LL;
typedef pair<long long int, long long int> pii;
typedef pair<double, double> pdd;

#define SORT(c) sort((c).begin(),(c).end())
#define BACKSORT(c) sort((c).begin(),(c).end(),std::greater<LL>())
#define FOR(i,a,b) for(LL i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)


int xcomp(vector<LL>& a, vector<LL>& b) {
	return a[0] < b[0];
}

#define XSORT(c) sort((c).begin(),(c).end(),xcomp)

#define ALL(x) (x).begin(),(x).end()
LL mod = 1000000007;

bool hantei(LL a, LL b) {
	if (a + 1 == b) {
		return true;
	}
	else
		if (a == b) {
			return true;
		}
		else
			if (a == b + 1) {
				return true;
			}
			else {
				return false;
			}
}

int main() {
	while (true)
	{
		LL  n;
		cin >> n;
		if (n == 0) {
			break;
		}

		vector<LL> num(n, 0);
		vector<LL> v(n, -9999);

		REP(i, n) {
			cin >> v[i];
		}
		REP(i, n - 1) {
			if (hantei(v[i], v[i + 1])) {
				num[i] = 2;
			}
		}

		bool flag = true;

		while (flag) {
			flag = false;

			REP(i, n) {
				LL hoge = num[i];
				if (i + num[i]<n) {
					if (hoge < num[i] + num[i + num[i]]) {
						hoge = num[i] + num[i + num[i]];
					}
				}
				if (i + 1<n) {
					if (i + num[i + 1] + 1<n) {
						if (hantei(v[i], v[i + num[i + 1] + 1])) {
							if (hoge < num[i + 1] + 2) {
								hoge = num[i + 1] + 2;
							}
						}a
					}
				}
				if (hoge != num[i]) {
					flag = true;
					num[i] = hoge;
				}
			}
		}


		vector<LL> fuga(n * 3, 0);

		for (int i = n - 1; i >= 0; --i) {
			fuga[i] = max(fuga[i + 1], num[i] + fuga[i + num[i]]);
		}

		cout << fuga[0] << endl;
	}

}

C++: #include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
using namespace std;
int n, a[1000], dp[1000][1000];
int main() {
	while (true) {
		cin >> n; if (n == 0)break; for (int i = 0; i < 1000; i++) { for (int j = 0; j < 1000; j++)dp[i][j] = 0; }
		for (int i = 0; i < n; i++)cin >> a[i];
		for (int i = 0; i < n - 1; i++) { if (abs(a[i] - a[i + 1]) <= 1) { dp[i][i + 1] = 1; } }
		for (int i = 2; i <= n; i++) {
			for (int j = 0; j < n; j++) {
				int a1 = j, a2 = i + j - 1; if (a2 >= n)continue;
				if (dp[a1][a2] == 0)continue;
				if (a2 < n - 2 && abs(a[a2 + 1] - a[a2 + 2]) <= 1)dp[a1][a2 + 2] = 1;
				if (a1 > 1 && abs(a[a1 - 1] - a[a1 - 2]) <= 1)dp[a1 - 2][a2] = 1;
				if (a1 > 0 && a2 < n - 1 && abs(a[a1 - 1] - a[a2 + 1]) <= 1)dp[a1 - 1][a2 + 1] = 1;
			}
		}
		for (int i = 0; i < n; i++) { for (int j = 0; j < n; j++) { if (dp[i][j] == 1)dp[i][j] = j - i + 1; } }
		for (int i = 1; i <= n; i++) {
			for (int j = 1; j <= n; j++) {
				for (int k = 0; k < n; k++) {
					int a1 = k, a2 = k + i, a3 = k + i + j; if (a3 > n)continue;
					dp[a1][a3 - 1] = max(dp[a1][a3 - 1], dp[a1][a2 - 1] + dp[a2][a3 - 1]);
				}
			}
		}
		cout << dp[0][n - 1] << endl;
	}
	return 0;
}

C++: #include <stdio.h>
#include <math.h>
#include<iostream>
#include<string>
#include<algorithm>
#include<set>
#include<map>
#include<vector>
#include<stack>
#include<queue>
#include<cmath>
#include<numeric>
using namespace std;




int main(){
    while(1){
        
        
        
        
    
    int n,a[500]={};
    cin>>n;
        if(n==0){break;}
    for(int i=0;i<n;i++){
        cin>>a[i];
    }
    bool j[500][500]={};
    for(int i=2;i<=n;i+=2){
        for(int t=0;t<=n-i;t++){
            if(abs(a[t]-a[t+i-1])<=1 && (j[t+1][t+i-2] || i==2)){j[t][t+i-1]=true; continue;}
            for(int h=t+1;h<t+i-1;h++){
                if(j[t][h] && j[h+1][t+i-1]){j[t][t+i-1]=true; break;}
            }
        }
    }
    int dp[500];
    fill(dp,dp+500,INT_MAX/2);
    dp[0]=1;
    for(int i=0;i<n;i++){
        if(j[0][i]){dp[i]=0;}
    }
    for(int i=1;i<n;i++){
        dp[i]=min(dp[i],dp[i-1]+1);
        for(int t=i;t<n;t++){
            if(j[i][t]){dp[t]=min(dp[t],dp[i-1]);}
        }
    }
    
    /*
    for(int i=0;i<n;i++){
        for(int t=0;t<n;t++){
            cout<<(j[i][t]?"1":"0")<<" ";
        }
        cout<<endl;
    }
     */
    
    //for(int i=0;i<n;i++){
        cout<<n-dp[n-1]<<endl;
    //}
    
    
        
    }
    
    return 0;
}

C++: #include <iostream>
#include <cmath>
#define REP(i, a, n) for(int i = ((int) a); i < ((int) n); i++)
using namespace std;

int N, W[300];
int dp[301][3001];

bool ok(int i, int j) {
  return abs(W[i] - W[j]) <= 1;
}

int dfs(int l, int r) {
  if(r - l <= 1) return 0;
  if(r - l == 2) return ok(l, l + 1) ? 2 : 0;
  if(dp[l][r] >= 0) return dp[l][r];

  int ret = 0;
  REP(i, l + 1, r) ret = max(ret, dfs(l, i) + dfs(i, r));
  if(ok(l, r - 1) && dfs(l + 1, r - 1) == r - l - 2) ret = max(ret, r - l);

  return dp[l][r] = ret;
}

int main(void) {
  while(cin >> N, N) {
    REP(i, 0, N) cin >> W[i];
    REP(i, 0, 301) REP(j, 0, 301) dp[i][j] = -1;
    cout << dfs(0, N) << endl;
  }
}