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

constexpr ll INF = 1LL<<60;

int main(){
	int N;
	cin >> N;
	vector<ll> A(N);
	for(int i=0; i<N; i++){
		cin >> A[i];
	}

	vector dp(N+1, vector<ll>(2, -INF));
	dp[1][0] = -A[0];
	for(int i=1; i<N; i++){
		for(int j=0; j<2; j++){
			if(dp[i][j]==-INF) continue;
			dp[i+1][j] = max(dp[i+1][j], dp[i][j]);

			if(j==0){
				dp[i+1][1] = max(dp[i+1][1], dp[i][0] + A[i]);
			}else{
				dp[i+1][0] = max(dp[i+1][1-j], dp[i][1] - A[i]);
			}
		}
	}

	cout << max(dp[N][0], dp[N][1]) << endl;

	return 0;
}