#include <bits/stdc++.h>
using namespace std;
#define task "main"
#define no "NO"
#define yes "YES"
#define F first
#define S second
#define vec vector
#define _mp make_pair
#define ii pair<int, int>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define evoid(val) return void(std::cout << val)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FOD(i, b, a) for(int i = (b); i >= (a); --i)
template<class X, class Y>
bool maximize(X &x, Y y) {
if (x < y) {
x = y;
return true;
}
return false;
}
const int MAX_N = (int)5e3 + 5;
int n;
int a[MAX_N];
namespace sub4 {
const int MAX_N = 505;
int dp[MAX_N][MAX_N];
bool mark[MAX_N * 5000];
void solve() {
memset(dp, 0, sizeof(dp));
FOR(l, 2, n) {
int curLength = 0;
FOR(r, l, n) {
int preLength = 0, res = 0;
FOD(i, l - 1, 1) {
if (mark[preLength]) res++;
maximize(dp[l][r], dp[i][l - 1] + res);
preLength += a[i];
}
curLength += a[r];
mark[curLength] = 1;
}
FOD(r, n, l) {
mark[curLength] = 0;
curLength -= a[r];
}
}
int ans = 0;
FOR(l, 1, n) maximize(ans, dp[l][n]);
cout << ans << "\n";
}
}
namespace sub5 {
int dp[MAX_N][MAX_N];
int f[MAX_N], sum[MAX_N];
void solve() {
memset(dp, 0, sizeof(dp));
sum[0] = 0;
FOR(i, 1, n) sum[i] = sum[i - 1] + a[i];
FOR(l, 2, n) {
f[0] = INT_MIN;
FOR(i, 1, l - 1) f[i] = max(f[i - 1], dp[i][l - 1]);
int i = l - 2, cnt = 0, res = 0;
FOR(r, l, n) {
dp[l][r] = res;
while (i > 0 && sum[r] + sum[i] > 2 * sum[l - 1]) i--;
if (i > 0 && sum[r] + sum[i] == 2 * sum[l - 1]) maximize(res, f[i] + (++cnt));
}
}
int ans = 0;
FOR(l, 1, n) maximize(ans, dp[l][n]);
cout << ans << "\n";
}
}
void solve() {
cin >> n;
FOR(i, 1, n) cin >> a[i];
// if (n <= 500) sub4::solve();
sub5::solve();
}
int32_t main() {
if (fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
bool multitest = 0;
int numTest = 1;
if (multitest) cin >> numTest;
while (numTest--) {
solve();
}
return 0;
}
/* Lak lu theo dieu nhac!!!! */
