#include<bits/stdc++.h>
using namespace std;
const int N=1e5+10;
long long a[N];
long long b[N];
int main(){
	int n=0;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	for(int i=1;i<=n/2;i++){
		if(a[i]!=a[n-i+1]){
			if(a[i]>=a[n-i+1]){
				b[i]=a[i]-a[n-i-1];
			}else{
				b[i]=a[n-i+1]-a[i];
			}
		}
	}
	int j=0;
	for(int i=1;i<=n/2;i++){
		if(b[i+1]!=0&&b[i]!=0){
			if(b[i+1]<=b[i]){
				j+=abs(b[i]);
				b[i+1]=0;
				b[i]=0;
			}else if(b[i+1]>b[i]){
				j+=abs(b[i]);
				b[i]=0;
				b[i+1]-=b[i];
			}
		}else{
			j+=abs(b[i]);
			b[i]=0;
		}
	}
	cout<<j;
	return 0;
}

求助，样例过了，全WA 蒟蒻不解