#include<stdio.h>
#include<algorithm>
using namespace std;
int main () {
	int n,v[800],i,nr=0,j;
	FILE *in=fopen("nrtri.in","r"), *out=fopen("nrtri.out","w");
	fscanf(in,"%d",&n);
	for(i=0;i<n;i++)
		fscanf(in,"%d",&v[i]);
	sort(v,v+n);
	for(i=1;i<n;i++)
		for(j=i+1;(v[i-1]+v[i])>=v[j]&&j<n;j++)
				nr++;
	fprintf(out,"%d\n",nr);
	fclose(in);
	fclose(out);
	return 0;
}