#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("avx,avx2,sse,sse2")
#include<bits/stdc++.h>
#define int long long
#define ll long long
#define down cout<<'\n';
#define NHP ios_base::sync_with_stdio(0);cout.tie(0);cin.tie(0);
#define modwwe int t;cin>>t; while(t--)
#define bit(i,j) (i>>j&1)
#define sobit(a) __builtin_popcountll(a)
#define task "test"
#define fin(x) freopen(x".inp","r",stdin)
#define fou(x) freopen(x".out","w",stdout)
#define pb push_back
#define checktime cerr << (double)clock() / CLOCKS_PER_SEC * 1000 << " ms";
using namespace std;
void phongbeo();
const int mod2=1e9+7;
const int mod1=998244353;
struct ib
{
int a;
int b;
};
struct icd
{
int a,b;
};
struct ic
{
int a,b,c;
};
struct id
{
int a,b,c,d;
};
int n,m,s2,s4,s3,sf,k,r,mid,s5,s6,mx,s7,s8,s9,mx2,res,dem2=0,dem=0,l;
int i,s10,s12;
int el=29;
main()
{
//#ifndef ONLINE_JUDGE
// fin(task),fou(task);
//#endif
NHP
//modwwe
// cin>>res;
phongbeo(),down
checktime
}
int a[5002];
int dp[5002][5002];
int dp2[5002];
void phongbeo()
{
cin>>n;/// hieu sai de cay vl
for(int i=1;i<=n;i++)
cin>>a[i];
for(int i=1;i<=n;i++)
a[i]+=a[i-1];
//cout<<a[i],down
for(int i=1;i<=n-1;i++)
{dp2[0]=-1e18;
for(int j=1;j<i;j++)
dp2[j]=dp[j][i];
for(int j=1;j<i;j++)
dp2[j]=max(dp2[j],dp2[j-1]);
l=i-1;
k=i;
s3=0;
s4=0;
s5=0;
// if(i==8)
//cout<<dp2[3],down
for(int j=i+1;j<=n;j++)
{ s4=a[j];
dp[i+1][j]=s5;
if(j==n+1) break;
/// dp[i][j]=max(dp[j],dp[j-1]);
// if(i==8) cout<<s3<<" "<<s2+s4<<" "<<s2<<" "<<s4<<" "<<a[i]<<" "<<k<<" "<<j,down
while(k>0&&a[k]+a[j]>a[i]*2)
{
k--;
}
if(a[k]+a[j]==a[i]*2&&k>0){
s3++;
s5=max(s5,s3+dp2[k]);
}
}
s7=max(s7,dp[i+1][n]);
/// cout<<dp[n]<<" "<<s3<<" "<<dp[4],down
}
cout<<s7;//<<" "<<dp[3][8];
}
