#include<bits/stdc++.h>
using namespace std;
int a[101],book[101];
int main()
{
int n,x,i,j,c=0;
cin>>n;
for(x=1;x<=n;x++)cin>>a[x];
for(x=1;x<=n;x++)
for(i=1;i<=n-1;i++)
for(j=i+1;j<=n;j++)
if(a[x]==a[i]+a[j])book[x]=1;
for(x=1;x<=n;x++)c=c+book[x];
cout<<c;
}