#include<cstdio>
#include<algorithm>
#define UP(a,b,c) for(int a=(b);a<=(c);a++)
using namespace std;
const int N=110;
int a[N];
int n,x;
int main(){
scanf("%d",&n);
UP(i,1,n)scanf("%d",&a[i]);
UP(k,1,n){
int f=0;
UP(i,1,n)UP(j,1,n)
if((i-j)*(j-k)*(k-i)!=0 && a[k]==a[i]+a[j])f=1;
x+=f;
}
printf("%d\n",x);
return 0;
}
#include<cstdio>
#include<algorithm>
#define UP(a,b,c) for(int a=(b);a<=(c);a++)
using namespace std;
const int N=110;
int a[N];
int n,x;
int main(){
scanf("%d",&n);
UP(i,1,n)scanf("%d",&a[i]);
sort(a+1,a+1+n);
UP(k,1,n){
int f=0;
UP(i,1,k-1)UP(j,i+1,k-1)
if(a[k]==a[i]+a[j])f=1;
x+=f;
}
printf("%d\n",x);
return 0;
}