#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int n,i,j,k,v[801],r;
char s[40001];

int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d\n",&n);
	gets(s);char *p=s;i=1;
	while (i<=n)
	{
		k=0;
		while (*p>='0' && *p<='9') k=k*10+*p-'0',++p;
		++p;v[i]=k;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]) r++;else
				k=n+1;
	printf("%d\n",r);
	return 0;
}