#include<cstdio>
#include<algorithm>
using namespace std;
 
FILE *f=fopen("nrtri.in","r");
FILE *g=fopen("nrtri.out","w");

int v[801];
int main(){
	int n,nr=0,i,j,k;
	
	fscanf (f,"%d",&n);
	for (i=1;i<=n;++i){
		fscanf (f,"%d",&v[i])
		;
	}
	
	sort (v+1,v+n+1);
	for (i=1;i<=n-2;++i){
		for (j=i+1;j<=n-1;++j){
			for (k=j+1;k<=n;++k){
				if (v[i]+v[j]>=v[k]){
					nr++;
				}
				else{
					break;
				}
			}
		}
	}
	
	fprintf (g,"%d",nr);
	
    return 0;
}