#include <bits/stdc++.h>
using namespace std;
int a[10001];
int main()
{
 iostream::sync_with_stdio(false);
 cin.tie(0);cout.tie(0);
 int n,cnt=0;
 cin >>n;int sump[200000],sumn[200000];
 for (int i=0;i<=199999;i++) {sump[i]=n;sumn[i]=n;}
 for (int i=1;i<=n;i++) cin >> a[i];
 
 for (int i=1;i<n;i++)
    for (int j=i;j<n;j++)
        if(a[i]+a[j]>=0) sump[a[i]+a[j]]=min(sump[a[i]+a[j]],j);
        else sumn[abs(a[i]+a[j])]=min(sumn[abs(a[i]+a[j])],j);
 for (int i=2;i<=n;i++)
    for (int j=1;j<i;j++)
    {int x=a[i]-a[j];
        if(x>=0&&sump[x]<i) {cnt++;break;}
        if(x<0&&sumn[abs(x)]<i) {cnt++;break;}
    }
 cout <<cnt;
}
 

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