CodeForces 731E Funny Game

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<ctime>
#include<iostream>
using namespace std;
typedef long long LL;
const double pi=acos(-1.0),eps=1e-10;
void File()
{
    freopen("D:\\in.txt","r",stdin);
    freopen("D:\\out.txt","w",stdout);
}
template <class T>
inline void read(T &x)
{
    char c = getchar();
    x = 0;
    while(!isdigit(c)) c = getchar();
    while(isdigit(c))
    {
        x = x * 10 + c - ‘0‘;
        c = getchar();
    }
}

long long sum[200010],a[200010];
long long maxf[200010],f[200010],ans,x;
int n;

int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++) cin>>a[i];
    for(int i=1;i<=n;i++) sum[i]=sum[i-1]+a[i];

    maxf[n]=f[n]=sum[n];
    f[n-1]=sum[n-1]-sum[n];
    maxf[n-1]=max(maxf[n],f[n-1]);
    x=-sum[n-1]+f[n];

    for(int i=n-2;i>=2;i--)
    {
        f[i]=min(sum[i]+x,sum[i]-sum[n]);
        maxf[i]=max(maxf[i+1],f[i]);
        x=min(x,-sum[i]+maxf[i+1]);
    }

    ans=f[n];
    for(int i=2;i<=n;i++) ans=max(ans,f[i]);
    cout<<ans<<endl;

    return 0;
}