#include <bits/stdc++.h>
using namespace std;
template<class T, class U>
void ckmin(T &a, U b)
{
if (a > b) a = b;
}
template<class T, class U>
void ckmax(T &a, U b)
{
if (a < b) a = b;
}
#define MP make_pair
#define PB push_back
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define FOR(i, a, b) for (auto i = (a); i < (b); i++)
#define FORD(i, a, b) for (auto i = (a) - 1; i >= (b); i--)
#define SZ(x) ((int) (x).size())
#define ALL(x) (x).begin(), (x).end()
const int MAXN = 5013;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vpi;
typedef vector<pll> vpl;
int N;
int arr[MAXN], pref[MAXN];
int dp[MAXN][MAXN];
int ans;
int fen[MAXN];
void update(int idx, int i)
{
for (int e = idx + 1; e <= i; e += e & (-e))
{
fen[e]++;
}
}
int query(int idx)
{
int res = 0;
for (int e = idx + 1; e; e -= e & (-e))
{
res += fen[e];
}
return res;
}
int32_t main()
{
ios_base::sync_with_stdio(false); cin.tie(0);
cout << fixed << setprecision(12);
cerr << fixed << setprecision(4);
cin >> N;
FOR(i, 0, N)
{
cin >> arr[i];
pref[i + 1] = pref[i] + arr[i];
}
// dp[0][0] = 0;
FOR(i, 2, N + 1)
{
fill(fen, fen + N + 2, 0);
set<int> cands;
int best = 0;
FOR(j, 1, i)
{
ckmax(dp[j][i - 1], dp[j - 1][i - 1]);
}
best = dp[i - 1][i - 1];
int iter = i - 1;
FOR(j, i, N + 1)
{
dp[i][j] = best;
int c = 2 * pref[i - 1] - pref[j];
while(iter != 0 && pref[iter] > c)
{
iter--;
}
if (pref[iter] == c)
{
update(i - iter, i);
ckmax(best, dp[iter][i - 1] + query(i - iter));
}
}
}
FOR(i, 1, N + 1)
{
ckmax(ans, dp[i][N]);
}
cout << ans << '\n';
return 0;
}
