#include <bits/stdc++.h>
using namespace std;
int n, a[55];

int f[55];//f[i]拿第i个苹果的最大值
int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	int res = 0;
	for (int i = 1; i <= n; i++) {
		f[i] = a[i];
		for (int j = 1; j < i - 1; j++) {
			f[i] = max(f[i], f[j] + a[i]);
		}
		res = max(res, f[i]);
	}
	cout << res << endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
const int N = 1e4 + 5;
int n, a[N];

int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	int res = 2, diff = a[2] - a[1], ans = 2;
	for (int i = 3; i <= n; i++) {
		if (a[i] - a[i - 1] == diff) {
			res++;
			ans = max(ans, res);
		} else {
			diff = a[i] - a[i - 1];
			res = 2;
		}
	}
	cout << ans << endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
	int n;
	cin>>n;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=i;j++){
			cout<<"#";
		}
		cout<<endl;
	}
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
int n, a[1000005], res = 0, m;

int main() {
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	sort(a + 1, a + n + 1);
	int now = a[1];
	for (int i = 2; i < n; i++) {
		if (a[i] - now < m)
			res++;
		else{
			now = a[i];
		}
	}
	cout << res << endl;
	return 0;
}

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

int main() {
	int n, res = 0;
	cin >> n;
	for (int a = 0; a * 2 <= n; a++) {
		for (int b = 0; b * 4 <= n; b++) {
			if (a * 2 + b * 4 > n)
				break;
			for (int c = 0; c * 8 <= n; c++) {
				if (a * 2 + b * 4 + c * 8 > n)
					break;
				for (int d = 0; d * 16 <= n; d++) {
					if (a * 2 + b * 4 + c * 8 + d * 16 > n)
						break;
					for (int e = 0; e * 32 <= n; e++) {
						if (a * 2 + b * 4 + c * 8 + d * 16 + e * 32 == n) {
							res++;
						}
					}
				}
			}
		}
	}
	cout << res << endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
int n, a[105];

int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	int res = 0;
	for (int i = 1; i < n; i++) {
		for (int j = 1; j < n; j++) {
			if (a[j] > a[j + 1]) {
				res++;
				swap(a[j], a[j + 1]);
			}
		}
	}
	for (int i = 1; i <= n; i++) {
		cout << a[i] << " ";
	}
	cout<<"\n";
	cout << res << endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
char mat[45][45];

int n, m, nxt[4][2] = {0, 1, 0, -1, 1, 0, -1, 0};
int book[45][45];

struct node {
	int x, y, cost;
};

int main() {
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			cin >> mat[i][j];
		}
	}
	queue<node>q;
	q.push({1, 1, 1});
	book[1][1] = 1;
	while (!q.empty()) {
		node tmp = q.front();
		q.pop();
		if (tmp.x == n && tmp.y == m) {
			cout << "YES" << endl;
			//cout<<tmp.cost<<endl;
			return 0;
		}
		for (int i = 0; i < 4; i++) {
			int nx = tmp.x + nxt[i][0];
			int ny = tmp.y + nxt[i][1];
			if (nx >= 1 && nx <= n && ny >= 1 && ny <= m) {
				if (book[nx][ny] == 0 && mat[nx][ny] != '#') {
					book[nx][ny] = 1;
					q.push({nx, ny, tmp.cost + 1});
				}
			}
		}
	}
	cout<<"NO"<<endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
const int N = 1e4 + 5;

int n, a[N], f[N][N]; //f[i][j]选的第i个结尾，第j个数倒数第二个
int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	f[2][1] = 2;
	for (int i = 3; i <= n; i++) {
		for (int j = 1; j < i; j++) {
			int diff = a[i] - a[j];
			for (int k = 1; k < j; k++) {
				int df = a[j] - a[k];
				if (diff != df)
					continue;
				f[i][j] = max(f[i][j], f[j][k] + 1);
			}
			//f[i][j] = f[j][k]+1
		}
	}
	int res = 0 ;
	for (int i = n; i >= 1; i--) {
		for (int j = 1; j < i; j++) {
			res = max(res, f[i][j]);
		}
	}
	cout << res << endl;
	return 0;
}