#include<cstdio>

 #include<iostream>

 using namespace std;

 int a[];

 int cnt;

 bool vis[];

 int main(){

     int n;

     scanf("%d", &n);

     for(int i = ; i <= n; i++){

         scanf("%d", &a[i]);

     }

     for(int i = ; i <= n; i++){

         for(int j = ; j <= n; j++){

             for(int k = j+; k <= n; k++){

                 if(vis[i] == )//注意标记，否则有重复

                     if(a[i] == a[j] + a[k]) cnt++, vis[i] = ;

             }

         }

     }

     printf("%d",cnt);

     return ;

 }