#include<iostream>
#include<algorithm>
using namespace std;

int optimalGameStrategy(int *a, int i, int j){

    if(i == j)
        return a[i];
    if(i == j+1)
        return max(a[i],a[j]);
    int piyush = max(a[i] + min(optimalGameStrategy(a, i + 2, j), optimalGameStrategy(a, i + 1, j - 1)) ,
    a[j] + min(optimalGameStrategy(a, i + 1, j - 1), optimalGameStrategy(a, i, j - 2)));

    return piyush;
}

int main(){
    int n;
    cin>>n;
    int *a = new int[n];
    cout<<optimalGameStrategy(a, 0, n - 1);

    return 0;
}