#include<fstream>
#include<algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");

int n,v[801];
int cautbin(int *v,int x){
	int low=0,high=n+1,mid;
    while (high - low > 1) {
        mid = (low + high) / 2;
        if (v[mid] < x) {
            low = mid;
        } else { // v[mid] >= x
            high = mid;
        }
    }
    if ( high ==n+1 || v[high]!=x) {
        return low;
    } else {
        return high;
    }
}
int main(){

cin>>n;
for(int i=1;i<=n;i++){
	cin>>v[i];
}
sort(v+1,v+n+1);
int k=0;
for(int i=1;i<n;i++){
	for(int j=i+1;j<=n;j++){
	
		int sm=(v[i]+v[j]);int e=cautbin(v,sm);
		if(sm>=v[e] && (v[j]+v[e])>=v[i] && (v[i]+v[e])>=v[j] && e!=i && e!=j){
			//cout<<i<<" "<<j<<" "<<e<<endl;
			k++;
		}
	
	}
}
cout<<k;
return 0;
}