#include <bits/stdc++.h>
using namespace std;

int main() {
	int n;
	cin>>n;
	vector<int> arr;
	int element;
	for(int i=0;i<n;i++)
	{
		cin>>element;
		arr.push_back(element);
	}
	int p1_score=0, p2_score=0;
	bool turn=1;
	bool reversed = false;
	int start=0, end=n-1;
	while(start <= end)
	{
		if(turn)
		{
			if(reversed){
				p1_score+=arr[end];
				end--;
			} 
			else{
				p1_score+=arr[start];
				start++;
			}
			turn=0;
		}
		else
		{
			if(reversed){
				p2_score+=arr[end];
				end--;
			} 
			else{
				p2_score+=arr[start];
				start++;
			}
			turn=1;
		}
	}
	cout<<p1_score-p2_score;
    return 0;
}