#include <bits/stdc++.h> using namespace std; using ll = long long; using ld = long double; #define fi first #define se second #define vi vector<int> #define vll vector<long long> #define pii pair<int, int> #define pll pair<long long, long long> #define pb push_back #define mp make_pair #define eb emplace_back #define all(x) (x).begin(), (x).end() #define sz(x) (int)(x).size() mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count()); mt19937_64 rng64(chrono::high_resolution_clock::now().time_since_epoch().count()); inline int rand(int l,int r){return uniform_int_distribution<int>(l, r)(rng);} inline ll rand(ll l,ll r){return uniform_int_distribution<ll>(l, r)(rng64);} #ifdef DEBUG auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";} auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";} #define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(X) #else #define debug(...){} #endif struct custom_hash { static uint64_t splitmix64(uint64_t x) { x += 0x9e3779b97f4a7c15; x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9; x = (x ^ (x >> 27)) * 0x94d049bb133111eb; return x ^ (x >> 31); } size_t operator()(uint64_t x) const { static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count(); return splitmix64(x + FIXED_RANDOM); } }; struct pair_hash{ size_t operator()(const pair<int,int>&x)const{ return hash<long long>()(((long long)x.first)^(((long long)x.second)<<32)); } }; const int MAXN = 5e3 + 7; int dp[MAXN][MAXN]; int dp2[MAXN][MAXN]; vector<pii> add[MAXN]; int ptr[MAXN]; int A[MAXN]; int pref[MAXN]; int n; void preprocessing(){ for(int i = 1; i <= n; i++){ pref[i] = pref[i - 1] + A[i]; } for(int i = 1; i <= n; i++){ int wsk = i - 1; int sum = A[i]; int wskR = i + 1; int sumR = A[i + 1]; while(wskR < n && wsk > 0){ if(sum == sumR){ add[i].pb(mp(wsk, wskR)); // cerr << i << ' ' << wsk << ' ' << wskR << '\n'; sum += A[wsk]; wsk--; wskR++; sumR += A[wskR]; continue; } if(sumR < sum){ wskR++; sumR += A[wskR]; }else{ sum += A[wsk]; wsk--; } } } } int main(){ ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL); cin >> n; for(int i = 1; i <= n; i++){ cin >> A[i]; } preprocessing(); for(int i = 1; i <= n; i++){ for(int j = 0; j <= i - 1; j++){ if(ptr[j]){ dp[i][j] = dp[add[j][ptr[j] - 1].se][j]; } while(ptr[j] < sz(add[j]) && add[j][ptr[j]].se < i){ dp[i][j] = max(dp[i][j], ptr[j] + 1 + dp2[j][add[j][ptr[j]].fi]); ptr[j]++; } //cerr << i << ' ' << j << ' ' << dp[i][j] << '\n'; dp2[i][j] = dp[i][j]; if(j){ dp2[i][j] = max(dp2[i][j], dp2[i][j - 1]); } } } cout << dp2[n][n - 1] << '\n'; return 0; }