#include <bits/stdc++.h>
using namespace std;
#define FOR(i, a, b) for(int i = a; i < b; ++i)
#define REP(i, n) FOR(i, 0, n)
#define _ << " " <<
#define pb push_back
#define fi first
#define se second
#define sz(c) (int)(c).size()
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define TRACE(x) cerr << #x << " " << x << endl
template<typename T1, typename T2>inline void minaj(T1 &x, T2 y) { x = (x > y ? y: x);}
template<typename T1, typename T2>inline void maxaj(T1 &x, T2 y) { x = (x < y ? y: x);}
typedef double lf;
typedef long long ll;
typedef pair<int, int> pii;
const int mod = 1e9 + 7;
int add(int x, int y) {x += y; if(x >= mod) return x - mod; return x;}
int sub(int x, int y) {x -= y; if(x < 0) return x + mod; return x;}
int mul(int x, int y) {return (ll) x * y % mod;}
const int MAXN = 5005;
int a[MAXN];
int dp[MAXN][MAXN];
int main() {
ios_base::sync_with_stdio(false); cin.tie(0);
int n; cin >> n;
REP(i, n) {
cin >> a[i];
}
REP(l, n) {
vector<int> prijelazi;
REP(x, l) {
prijelazi.push_back(dp[x][l - 1]);
}
reverse(prijelazi.begin(), prijelazi.end());
prijelazi.push_back(-MAXN);
for (int i = prijelazi.size() - 2; i >= 0; --i) {
maxaj(prijelazi[i], prijelazi[i + 1]);
}
int delta = 0;
int best = 0;
int up = 0, down = 0;
int i = l - 1, j = l;
do {
int du = -1;
int dd = -1;
if (i >= 0) {
du = up + a[i];
}
if (j < n) {
dd = down + a[j];
}
if (du == -1) {
dp[l][j] = best;
down += a[j];
j ++;
continue;
}
if (dd == -1) {
break;
}
if (dd < du) {
dp[l][j] = max(best, delta + prijelazi[l-i-1]);
down += a[j];
j ++;
}
else if (du < dd) {
if (i) maxaj(best, dp[i-1][l-1] + delta);
up += a[i];
i --;
}
else {
dp[l][j] = max(best, delta + prijelazi[l-i-1]);
delta ++;
down += a[j];
j ++;
}
} while (j < n);
}
int sol = 0;
REP(i, n) {
maxaj(sol, dp[i][n-1]);
}
cout << sol << endl;
}
