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

int maxProfit(vector<int>& prices) {
    int i = 0,j = 0,n = prices.size(),k = 2;
    if(n < 2)
        return 0;
    vector<vector<int>> cash(n, vector<int>(k + 1,0));
    vector<vector<int>> hode(n, vector<int>(k + 1,INT_MIN));
    for(j = k;j > 0;j--){
        cash[i][j] = max(hode[0][j] + prices[i],cash[0][j]);
        hode[i][j] = max(hode[0][j],cash[i][j - 1] - prices[i]);
    }
    for(i = 1;i < n;i++){
        for(j = k;j > 0;j--){
           cash[i][j] = max(hode[i-1][j] + prices[i],cash[i - 1][j]);
           hode[i][j] = max(hode[i-1][j],cash[i - 1][j - 1] - prices[i]);
        }
    }
    return cash[n - 1][k];
}

int main(){
    int n,p;
    cin >> n;
    vector<int>prices(n);
    for(int i = 0;i < n;i ++){
        cin >> p;
        prices[i] = p;
    }
    cout << maxProfit(prices);
    return 0;
}