为什么不对呀QAQ

#include<bits/stdc++.h>
#define re register
#define int long long
using namespace std;
const int maxn=1<<9;
int n,m,dp[11][maxn][91],st[maxn],cnt,ext[maxn],num[maxn],ans(0);
signed main(){
	std::ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
    cin>>n>>m;
    for(re int i(0);i<(1<<n);i=-~i){
        if(!(i&(i>>1))&&!(i&(i<<1))) st[++cnt]=i;
        ext[i]=i|(i<<1);
        num[i]=num[i>>1]+(i&1);
    }
    dp[0][0][0]=1;
    for(re int i(1);i<=n;i=-~i){
        for(re int j(0);j<cnt;j=-~j){
            for(re int k(0);k<=m;k=-~k){
                if(dp[i-1][j][k]){
                    for(re int l(0);l<cnt;l=-~i){
                        if((ext[st[j]]&ext[st[l]])==0) dp[i][l][k+num[st[l]]]+=dp[i-1][j][k];
                    }
                }
            }
        }
    }
    for(re int i(0);i<cnt;i=-~i){
        ans+=dp[n][i][m];
    }
    cout<<ans;
    return 0;
}