Apoint Substring

#include <bits/stdc++.h>
using namespace std;
int n;
int qs[1010];
int dp[1010][1010];
int subs(int f,int b){
    if(f==b) return 0;
    if(dp[f][b]!=0) return dp[f][b];
    int sf=/*front*/(qs[f]-qs[f-1])+/*Qs front+1->back*/(qs[b]-qs[f])+/*x2 min*/min((qs[f]-qs[f-1]),(qs[b]-qs[f]));
    int sb=/*back*/(qs[b]-qs[b-1])+/*Qs front->back-1*/(qs[b-1]-qs[f-1])+/*x2 min*/min((qs[b]-qs[b-1]),(qs[b-1]-qs[f-1]));
    return dp[f][b]=max(sf+subs(f+1,b),sb+subs(f,b-1));
}

int main(){
    int m;
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        scanf("%d",&m);
        qs[i]=qs[i-1]+m;
    }
    int ans=subs(1,n);
    printf("%d",ans);
}