#include <cstdio>
#include <algorithm>
#define nr 801
using namespace std;
int main()
{
	int n, a[nr], cont=0, i, j, k;
	FILE *f=fopen("nrtri.in","r");
	FILE *g=fopen("nrtri.out","w");
	fscanf(f,"%d",&n);
	for(int i=1; i<=n; i++) 
		fscanf(f,"%d",&a[i]);
	sort(a+1,a+n+1);
	for(i=1;i<=n;i++)
		for(j=i+1;j<=n;j++)
			for(k=j+1;k<=n;k++)
				if(a[i]+a[j]>=a[k]) 
					cont++;
				else 
					break;
    fprintf(g, "%d\n",cont);
	return 0;
}