蒟蒻不會四邊形不等式

形如

#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cstring>
using namespace std;
typedef long long ll;

inline char nc(){
  static char buf[100000],*p1=buf,*p2=buf;
  if (p1==p2) { p2=(p1=buf)+fread(buf,1
 
,100000,stdin); if (p1==p2) return EOF; }
  return *p1++;
}

inline void read(int &x){
  char c=nc(),b=1;
  for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1;
  for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b;
}

const int N=2005;

int n;
int a[N]; ll sum[N];
ll f[N][N]; int
 
 s[N][N];

inline ll w(int l,int r){
  return sum[r]-sum[l-1];
}

int main(){
  freopen("t.in","r",stdin);
  freopen("t.out","w",stdout);
  read(n); for (int i=1;i<=n;i++) read(a[i]),a[n+i]=a[i]; n<<=1;
  for (int i=1;i<=n;i++) sum[i]=sum[i-1]+a[i];
  memset(f,0x3f,sizeof(f));
  for (int i=1
 
;i<=n;i++) f[i][i]=0,s[i][i]=i;
  for (int i=2;i<=n/2;i++)
    for (int l=1;l+i-1<=n;l++){
      int r=l+i-1;
      for (int k=s[l][r-1];k<=s[l+1][r];k++)
    if (f[l][r]>f[l][k]+f[k+1][r]+w(l,r))
      f[l][r]=f[l][k]+f[k+1][r]+w(l,r),s[l][r]=k;
    }
  ll ans=1LL<<30;
  for (int i=1;i<=n/2;i++)
    ans=min(ans,f[i][i+n/2-1]);
  printf("%lld\n",ans);
  return 0;
}